Monoclonal Antibodies and Methods of Use

ABSTRACT

This disclosure relates to immunogens and monoclonal antibodies useful in the identification and/or treatment of cancer cells, including those of the dog. In one example, chimeric anti-canine CD20 antibodies are provided. The antibodies can be used therapeutically to treat lymphoma in dogs.

FIELD OF THE DISCLOSURE

The technology relates to immunogens, and to binding agents that bindthe immunogens, like monoclonal antibodies, for identification orisolation of cancer cells that contain the immunogens, or treatment orprevention of cancers containing the cancer cells, especially in dogs.

BACKGROUND INFORMATION

Binding agents like monoclonal antibodies are useful in diagnosis andtreatment of diseases like cancer, in canines (dogs), for example, atype of cancer is B cell lymphoma in which uncontrolled B cellproliferation can lead to illness and death. Lymphoma also occurs inhumans and may be treated with anti-human. CD20 antibodies, like.Rituximab, for example. These antibodies, that react with or bind humanCD20, generally do not bind canine CD20 (Jubala et al., Vet Pathol July;42(4):468-76, 2005; Impellizeri et al., Vet. J., May; 171(3):556-8,2006; Gravanis et al., The Oncologist, December; 15:1335-1343, 2010).Accordingly, binding agents capable of interacting with CD20 on thesurface of canine B cells are desired. The technology described hereinprovides these reagents and therapeutics, as shown below.

SUMMARY OF THE DISCLOSURE

In certain embodiments, this disclosure relates to reagents and methodsfor preventing and/or treating canine disease conditions (e.g.,lymphoma). For example, epitopes of canine CD20 have been identifiedthat may be targeted to deplete canine blood and/or tissues of B celllymphoma cells. Immunogens have been identified, as described herein,that may be used to induce and/or enhance an immune response (e.g., theproduction of antibodies) suitable for use in preventing and/or treatingthese diseases. Nucleic acids encoding the immunogens and thepolypeptide/peptide immunogens per se, and methods for making the sameare also described. In certain embodiments, the immunogens are orcontain particular epitopes of interest such as LIKAPMPYV (SEQ IDNO.: 1) and/or DIHNCD (SEQ ID NO.: 2). These immunogens may be usedalone and/or with other immunogens and/or “backbones” (e.g., a canineFc) to induce and/or enhance an immune response against canine CD20, forexample.

In certain embodiments, this disclosure provides binding agents usefulin the isolation and/or identification of cells expressing canine CD20or cells that contain a cell surface protein that reacts with thesebinding agents (e.g., B cells, B lymphoma cells, canine CD20), and/ortreatment and prevention of cancer in a mammal (e.g., a canine). Incertain embodiments, the binding agent may be an antibody reactiveagainst canine CD20 expressed on a cell surface. In some embodiments,the one or more binding agents (e.g., an antibody, like a monoclonalantibody) binds to or reacts with canine CD20 at a region thereof whichcomprises the amino acid sequences, or epitope(s), LIKAPMPYV (SEQ IDNO.: 1) and/or DIHNCD (SEQ ID NO.: 2).

In other embodiments, methods for detecting canine cells using thesebinding agents are provided. In certain embodiments, cells expressingCD20 on their cell surface (e.g., B cell lymphoma) in an animal (e.g., acanine) can be identified and/or isolated by contacting a testbiological sample containing the cells with the binding agent anddetecting the binding agent bound to the biological sample or componentsthereof (e.g., lymphoma cells). In certain embodiments, the method mayinclude comparing the amount of binding in the test biological sample tothe amount of binding in a control biological sample, wherein increasedbinding to the test biological sample relative to the control biologicalsample may indicate the presence of one or more lymphoma cells in thetest biological sample. In some embodiments, the biological sample iscanine blood or a needle aspirate. These methods are also provided in anin vivo and or in vitro format.

In some embodiments, methods for eliminating cells expressing canineCD20 using such binding agents are also provided. Methods for treatingone or more disease conditions (e.g., lymphoma) in an animal (e.g.,canine) by administering to the animal at least one or more effectivedoses of binding agent or derivative thereof are also provided. In someembodiments in which the binding agent is a monoclonal antibody, themonoclonal antibody may be administered in a dosage amount of about 1 toabout 50 mg/kg of animal body weight, about 1 to about 30 mg/kg, orabout 5 to about 30 mg/kg (e.g., about 10 m/kg). The binding agents maybe administered more than once over a period of time. In someembodiments, the binding agent may be administered in conjunction withone or more other agents (e.g., chemotherapeutic agents).

Also provided are kits for using the binding agents to identify ordetect polypeptides and/or cells reactive therewith, and/or for usingsuch binding agents to prevent and or treat disease (e.g., caninelymphoma). The kit may comprise, for example, a binding agent orderivative thereof in any form (e.g., in solution, lyophilized) alongwith, optionally, instructions for use. Other embodiments will be clearfrom the descriptions provided herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. FACS affinity analysis of binding of monoclonal antibodies tocanine B-cell lymphoma cells.

FIG. 2. A. Alignment of canine and human extracellular domains of CD20and human/canine hybrid variants V1-V4. B. ELISA binding analysis ofhybridoma antibodies 1E4, 1G1, and 1G10 to canine CD20 ECD2 and V1-V4.

FIG. 3. FACS analysis of binding of hybridoma antibody 1E4 to canineperipheral blood mononuclear cells (PBMC).

FIG. 4. A. SDS-PAGE analysis of purified chimeric anti-canine CD20antibody 1E4-cIGB expressed from CHO cells. B. Size exclusionchromatography analysis of purified 1E4-cIgCB.

FIG. 5. ELISA analysis of binding to CD20 ECD2 peptide of increasingconcentrations of unmodified (WT) 1E4-cIgGB antibody and antibodies withthe indicated amino acid substitutions to the NG sequence within V_(L)of 1E4-cIgGB.

FIG. 6. Dose-dependent in vivo depletion of canine B cells usingexemplary antibody 1E4-cIgGB, Rituxan-cIgGB was included as a negative(isotype) control.

DETAILED DESCRIPTION Binding Agents

This disclosure relates to binding agents that bind canine CD20 on thesurface of cells in vitro and/or in vivo. The binding agents may alsobind isolated canine CD20 polypeptide and/or fragments and/orderivatives thereof. Also provided are methods, for diagnosing, treatingand/or preventing one or more diseases associated with the existence ofcells expressing canine CD20. For instance, the binding agents may beantibodies (e.g., monoclonal antibodies) that may react with and or bindto the epitopes SEQ ID NOS.: 1 and 1 or 2. These monoclonal antibodiesmay comprise any one or more of the amino acid sequences shown in Tables1 and 4-5, for example, (and/or one or more fragments and/or derivativesthereof) and may be encoded by any one or more of the nucleotidesequences shown therein (and/or one or more fragments and/or derivativesthereof). This disclosure also provides for the use of these monoclonalantibodies to isolate, identify, and or target cells expressing canineCD20 (e.g., canine B cell lymphoma cells) for inhibition (e.g.,cytotoxicity) for the prevention and/of treatment of cancer in animals(e.g., canines). In certain embodiments, these monoclonal antibodies maybe reactive against canine CD20 expressed on the surface of cells.

Binding agents generally interact with or bind specifically with atarget. For example, the binding agents disclosed herein generallyinteract specifically with regions of canine CD20 as a target. Binding“specifically” to CD20 means that the amount of binding to CD20 is morethan the amount of binding to non CD20 targets (i.e., there may bebackground nonspecific binding). Generally, specific binding of bindingagents to a protein, for example, may be achieved by binding to aspecific sequence of amino acids within a protein target. Thesesequences may be referred to as epitopes. Molecules containing theepitopes may be used to stimulate binding agents like antibodies and maybe referred to as immunogens. The binding agents may also recognizespecific 2- and/or 3-dimensional structures as part of the epitope. Inone example, monoclonal antibodies disclosed herein may bind to epitopesof canine CD20, LIKAPMPYV (SEQ ID NO.: 1) and/or DIHNCD (SEQ ID NO.: 2).

The specific interaction or binding of a binding agent with its targetis thought to be a type of equilibrium reaction. In one example, thespecific binding can be quantified. The quantification may use adissociation constant, or K_(d). K_(d) is known in the art to be a typeof equilibrium constant that describes the propensity of, in this case,an antibody to separate from the antigen or epitope to which it hasbound. Thus, describes the affinity that an antibody has for an epitope.The lower the K_(d), the higher is the affinity of a binding agent forits target.

In certain embodiments, the binding agent is a monoclonal antibodyselected from the group consisting of 1E4, 1G10, and 1G1, as describedherein. The monoclonal antibody may comprise the amino acid sequence ofany one or more of SEQ ID NOS.: 3, 6, 9, 11, 13, and or 15 (e.g., as inTable 1), and/or any one or more fragments and/or derivatives thereof.The antibodies may contain any of the CDR sequences set forth in Table4, The antibody (e.g., monoclonal antibody) may also be of any suitableisotype or isotype subclass. In certain embodiments, the antibody has acanine IgG subclass of, for example, IgGA, IgGB (e.g., SEQ ID NOS.: 55or 57; Table 5), IgGC, and/or IgD as described in Tang et al., VetImmunol Immunopathol., August; 80(3-4):259-70, 2001.

The binding agent may also be a derivative of an antibody (of, forexample, the monoclonal antibody 1E4, 1G10, and/or 1G1) such as, forexample, a Fab, F(ab′)₂, Fab′ single chain antibody, Fv, single chain,mono-specific antibody, bi-specific antibody, tri-specific antibody,multi-valent antibody, chimeric antibody, canine-human chimericantibody, canine-mouse chimeric antibody, antibody comprising a canineF_(c), humanized antibody, human antibody, caninized, CDR-graftedantibody, shark antibody, nanobody (e.g., antibody consisting of asingle monomeric variable domain), camelid antibody (e.g., from theCamdidae family) microbody, intrabody (e.g., intracellular antibody),and or de-fucosylated antibody and/or derivative thereof. Mimeties ofbinding agents and/or antibodies are also provided. The binding agentmay also comprise a detectable label and/or effector moiety fixablyattached thereto.

Isolated polynucleotides encoding suitable binding agents are alsoprovided. These polynucleotides may comprise, for example, any one ormore of SEQ ID NOS.: 4, 5, 7, 8, 10. 12, 14, and/or 16 (e.g., Table 1),and/or any one or more fragments and or derivatives thereof. In certainembodiments, expression vectors and or host cells comprising thesepolynucleotides and/or encoding and or expressing these polypeptides arcalso provided.

Compositions comprising these binding agents, polypeptides, peptides,polynucleotides, expression vectors, and/or host cells are also providedin some embodiments. In certain embodiments, the compositions comprise apharmaceutically acceptable carrier.

The monoclonal antibodies disclosed here (designated as “A” antibodiesfor this example), that bind to a specific epitope or epitopes, maycompete for binding with other antibodies (designated as “B” antibodiesfor this example) that recognize the same or similar epitopes, or thatrecognize epitopes that are in proximity to the epitopes recognized bythe “A” antibodies (e g., overlapping epitopes). Competition means thatone of the antibodies binds at the expense of the other antibody, or atleast inhibits binding of the other antibody to a degree. For example,an “A” antibody that decreases or prevents binding of a “B” antibody issaid to compete with “B” for binding. These “B” antibodies are alsoexamples of antibodies that are part of the invention disclosed here.Competition between “A” and “B” antibodies for binding to their epitopesmay be measured using so-called competition experiments. Generally, incompetition experiments, the binding agents that are to be compared areadded to placed in proximity with, the target to which the bindingagents are capable of binding or suspected of binding. The experimentsare designed so it is possible to quantify binding of the individualbinding agents to the target. Competition is found, for example, whenaddition of at least one “A” antibody results in binding of a “B”antibody to a lesser degree than if the, “A” antibody were not present.In one example, binding agent “A” competes with binding agent “B” forbinding to the target, “B” may also compete with “A.” The “A” and “B”antibodies may or may not have substantially similar K_(d)'s.

Where the binding agent is an antibody, it may be identified withreference to the nucleotide and/or amino acid sequence corresponding tothe variable and/or complementarity determining regions (“CDRs”)thereof. For instance, an exemplary binding agent that is, is derivedfrom, or is related to the monoclonal antibody 1E4, 1G10, or 1G1 maycomprise a heavy and/or a light chain that each comprise one or moreconstant and or variable regions. The variable regions typicallycomprise one or more CDRs that in large part determine the bindingspecificity of the antibody. These monoclonal antibodies may beidentified by analysis of the nucleotide sequences encoding the variableregions. The monoclonal antibodies may also be identified by analysis ofthe amino acid sequences of (e.g., which may be encoded by thenucleotide sequences) the variable regions. For instance, exemplaryamino acid sequences of the light and heavy chain variable regions of1E4, 1G10, and 1G1, and exemplary nucleotide sequences encoding thesame, are shown below:

TABLE 1 Description Sequence Light chain variableDVVMTQNPLSLPVSLGDQASISCRSSQSLIYNNGNTYLHWYRQ region (V_(L)) of 1E4KPGQSPKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVEAEDLGVYFCSQSTHVPFTFGSGTKLEIK (SEQ ID NO.: 3) Nucleotide sequenceGATGTTGTGATGACCCAAAACCCACTCTCCCTGCCTGTCAGTC encoding SEQ IDTTGGAGATCAAGCCTCCATCTCTTGCAGATCTAGTCAGAGCCT NO.: 3 (1E4, V_(L))TATATACAATAATGGAAACACCTATTTACATTGGTACCGGCAGAAGCCAGGCCAGTCTCCAAAGCTCCTGATCTACAAAGTTTCCAACCGATTTTCTGGGGTCCCAGACAGGTTCAGTGGCAGTGGATCAGGGACAGATTTCACACTCAAGATCAGCAGAGTGGAGGCTGAGGATCTGGGAGTTTATTTCTGCTCTCAAAGTACACATGTTCCATTCACGTTCGGCTCGGGGACAAAGTTGGAAATAAAA (SEQ ID NO.: 4) Codon-optimizedGATGTCGTGATGACTCAGAATCCACTGTCCCTGCCTGTGTCCC nucleotide sequenceTGGGCGATCAGGCTTCCATTAGCTGTCGTTCCTCTCAGTCCCT encoding SEQ IDGATCTACAACAATGGTAACACCTACCTGCACTGGTATAGACAG NO.: 3 (1E4, V_(L))AAGCCCGGCCAGTCCCCTAAGCTGCTGATCTACAAAGTGAGTAATAGGTTCTCAGGAGTCCCAGACCGGTTTTCCGGCAGCGGATCTGGGACCGATTTCACACTGAAAATCTCTAGGGTGGAGGCCGAAGACCTGGGCGTCTACTTTTGTAGTCAGAGCACTCACGTCCCCTTCACCTTCGGCAGCGGAACAAAACTGGAAATCAAG (SEQ ID NO: 5) Heavy chain variableEVQLVESGGGLVKPGGSLKLSCAASGFTFSDYGMLWVRQAPEK region (V_(H)) of 1E4GLEWIAYISSGSSTIYYADRVKGRFTISRDNAKNTLFLQMTSLRSEDTAMYYCSTGTFAYWGQGTPVTVSS (SEQ ID NO.: 6)  Nucleotide sequenceGAGGTGCAGCTGGTGGAGTCTGGGGGAGGCTTAGTGAAGCCTG encoding SEQ IDGAGGGTCCCTGAAACTCTCCTGTGCAGCCTCTGGATTCACTTT NO.: 6 (1E4, V_(H))CAGTGACTATGGAATGCTCTGGGTTCGTCAGGCTCCAGAGAAGGGGCTGGAGTGGATTGCATACATTAGTAGTGGCAGTAGTACCATCTACTATGCAGACAGAGTGAAGGGCCGATTCACCATCTCCAGAGATAATGCCAAGAACACCCTGTTCCTGCAAATGACCAGTCTGTTGCTTACTGGGGCCAAGGGACTCCGGTCACTGTCAGCTCA (SEQ ID NO.: 7)Codon-optimized GAGGTGCAGCTGGTGGAGTCTGGTGGTGGTCTGGTCAAGCCTGnucleotide sequence GAGGTTCCCTGAAACTGAGTTGTGCCGCATCTGGGTTTACATTencoding SEQ ID CTCTGACTACGGAATGCTGTGGGTGAGGCAGGCACCAGAGAAGNO.: 6 (1E4, V_(H)) GGCCTGGAATGGATCGCTTATATTTCCAGCGGATCTAGTACTATCTACTATGCAGACAGGGTCAAGGGCCGGTTCACCATTAGCAGAGATAACGCCAAAAATACCCTGTTTCTGCAGATGACATCACTGAGGTCCGAGGATACCGCTATGTATTATTGCTCCACAGGGACTTTTGCTTACTGGGGACAGGGGACACCCGTGACCGTCAGCTCA (SEQ ID NO.: 8) Light chainDIVMTQAAPSVPVTPGESVSISCRSNKSLLHRNGNTYLYWFLQ variable regionRPGQSPQLLIYRMSNLASGVPDRFSGSGSGTAFTLRISRVEAE (V_(L)) of 1G10DVGVYYCMQHLEFPFTFGGGTKLEIK (SEQ ID NO.: 9) Nucleotide sequenceGATATTGTGATGACTCAGGCTGCACCCTCTGTACCTGTCACTC encoding SEQ IDCTGGAGAGTCAGTATCCATCTCCTGCAGGTCTAATAAGAGTCT NO.: 9 (1G10, V_(L))CCTGCATCGTAATGGCAACACTTACTTGTATTGGTTTCTGCAGAGGCCAGGCCAGTCTCCTCAGCTCCTGATATATCGGATGTCCAATCTTGCCTCAGGAGTCCCAGACAGATTCAGTGGCAGTGGGTCAGGAACTGCTTTCACACTGAGAATCAGTAGAGTGGAGGCTGAGGATGTGGGTGTTTATTACTGTATGCAACATCTGGAATTTCCTTTCACGTTCGGCGGGGGGACCAAGCTGGAAATAAAA (SEQ ID NO.: 10) Heavy chainEVQLQQSGPELVKPGASVKISCKASGYTFTDYYMNWVKQSHGK variable regionSLEWIGDINPNNGDTSYNQKFKGKAPLTVDKSSSTAYMEVRSL (V_(H)) of 1G10TSEDSAVYFCARGGVLRYPYYYVMDYWGQGTSVTVSS (SEQ ID NO.: 11)Nucleotide sequence GAGGTCCAGCTGCAACAATCTGGACCTGAGCTGGTGAAGCCTGencoding SEQ ID GGGCTTCAGTGAAGATATCCTGTAAGGCTTCTGGATACACGTTNO.: 11 (1G10, V_(H)) CACTGACTACTACATGAACTGGGTGAAGCAGAGCCATGGAAAGAGCCTTGAGTGGATTGGAGACATTAATCCTAACAATGGTGATACTAGCTACAACCAGAAATTCAAGGGCAAGGCCCCCTTGACTGTAGACAAGTCCTCCAGCACAGCCTACATGGAGGTCCGCAGCCTGACATCTGAGGACTCTGCAGTCTATTTCTGTGCAAGAGGAGGAGTACTACGGTACCCGTATTACTATGTTATGGACTACTGGGGTCAAGGAACCTCAGTCACTGTCAGCTCA (SEQ ID NO.: 12) Light chainDIVMTQSQKFMSRSVGDRVSVTCKASQNVGPNVAWYQQRPGQS variable regionPKPLIYSASYRYSGVPDRFTGSGSGTDFTLTISNVQSEDLAEY (V_(L)) of 1G1FCQQYNNYPYTFGGGTKLEIK (SEQ ID NO.: 13) Nucleotide sequenceGACATTGTGATGACCCAGTCTCAAAAATTCATGTCCAGATCAG encoding SEQ IDTAGGAGACAGGGTCAGCGTCACCTGCAAGGCCAGTCAGAATGT NO.: 13 (1G1, V_(L))GGGTCCTAATGTAGCCTGGTATCAACAGAGACCAGGGCAATCTCCTAAACCACTGATTTACTCGGCATCCTACCGGTACAGTGGAGTCCCTGATCGCTTCACAGGCAGTGGATCTGGGACAGATTTCACTCTCACCATCAGCAATGTGCAGTCTGAAGACTTGGCAGAGTATTTCTGTCAGCAATATAACAACTATCCGTACACGTTCGGAGGGGGGACCAAGCTGGAAATAAAA (SEQ ID NO.: 14) Heavy chainEVQLQQSGAELVRPGASVKLSCTASGFNIKDDYMHWVKQRPEQ variable regionGLEWIGWIDPENGHTKYASKFQGKATITADTSSNTAYLQLSSL (V_(H)) of 1G1TSEDTAVYYCTSLRHYYGSSYVSPHYYWGQGTTLTVSS (SEQ ID NO.: 15)Nucleotide sequence GAGGTTCAGCTGCAGCAGTCTGGGGCTGAGCTTGTGAGGCCAGencoding SEQ ID GGGCCTCAGTCAAGTTGTCCTGCACAGCTTCTGGCTTTAATATNO.: 15 (1G1, V_(H)) TAAAGACGACTATATGCACTGGGTGAAGCAGAGGCCTGAACAGGGCCTGGAGTGGATTGGATGGATTGATCCTGAGAATGGTCATACTAAATATGCCTCGAAGTTCCAGGGCAAGGCCACTATAACAGCAGACACATCCTCCAACACAGCCTACCTGCAGCTCAGCAGCCTGACATCTGAGGACACTGCCGTCTATTACTGTACTTCCCTCCGGCATTACTACGGTAGTAGCTACGTATCGCCCCATTACTACTGGGGCCAAGGCACCACTCTCACTGTCAGCTCA (SEQ ID NO.: 16)

Any of the amino acids shown in Table 1 (and/or any one or morefragments and/or derivatives thereof) may also be substituted by anyother amino acid as desired by one of ordinary skill in the art. Forexample, one of skill in the art may make conservative substitutions byreplacing particular amino acids with others as shown in Table 7 below.Exemplary amino acids that may be substituted may include, for example,residues 26, 28, 33, and/or 34 of SEQ ID NO.: 9 (1G10 light chainvariable region); residues 55 and/or 56 of SEQ ID NO.: 11 (1G10 heavychain variable region); and/or residues 52, 53, 55 and/or 56 of SEQ IDNO.: 15 (1G1 heavy chain variable region), which may be substituted withany other amino acid including but not limited to the conservativesubstitutions shown in Table 7 below. Nucleotide sequences encoding theconservative amino acid substitutions may be designed using the geneticcode as set forth in Table 6. Examples of such substituted amino acidsequences include, for instance:

-   DIVMTQAAPSVPVTPGESVSISCRSXKXLLHRXXNTYLYWFLQRPGQSPQLLIYR    MSNLASGVPDRFSGSGSGTAFTLRISRVEAEDVGVYYCMQHLEFPFTFGGGTKLE IK (SEQ ID    NO.: 17) where X is any amino acid (modification of 1G10 light chain    variable region indicated by SEQ ID NO.: 9);-   EVQLQQSGPELVKPGASVKISCKASGYTFTDYYMNWVKQSHGKSLEWIGDINPN    XXDTSYNQKFKGKAPLTVDKSSSTAYMEVRSLTSEDSAVYFCARGGVLRYPYY    YVMDYWGQGTSVTVSS (SEQ ID NO.: 18) where X is any amino acid    (modification of 1G10 heavy chain variable region indicated by SEQ    ID NO.: 11; and,-   EVQLQQSGAELVRPGASVKLSCTASGFNIKDDYMHWVKQRPEQGLEWIGWIXX    EXXHTKYASKFQGKATITADTSSNTAYLQLSSLTSEDTAVYYCTSLRHYYGSSY    VSPHYYWGQGTTLTVSS (SEQ ID NO.: 19) where X is any amino acid    (modification of 1G1 heavy chain variable region indicated by SEQ ID    NO.: 15.

Any of the amino acid sequences shown in Table 1, and/or any fragmentsand/or derivatives thereof may also he combined with any other variableregion and/or CDR in any order and/or combination to form hybrid, and orfusion binding agents and/or inserted into other heavy and/or lightchain variable regions using standard techniques. These may be used inconjunction with any constant regions e.g., as in Table 5).

CDRs (complementarity-determining regions) are amino acid sequences fromantibodies that are, at least in part, responsible for binding of anantibody to a specific target. It is understood by those of skill in theart that CDRs may be identified using any of several techniques and/orschemes. CDRs of the binding agents shown herein may be identified usingany of these techniques. For instance, one of ordinary skill in the artmay identify CDRs using the Kabat Numbering Scheme, the ChothiaNumbering Scheme, the Enhanced Chothia Numbering Scheme, and/or any ofthe available CDR Definition Schemes (e.g., AbM, contact definition, andor as described by MacCullum, et al., J. Biol., 262(5):732-745, 1996. Asummary of various schemes, in part based on, for example, Kabat et al.,“Sequences of Proteins of Immunological. Interest,” 5th Ed., PublicHealth Service, National institutes of Health, Bethesda, Md., NIHpublication No. 91-3242 (1991), and Al-Lazikani et al., “Standardconformations for the canonical structures of immunoglobulins,” J. Mol.Biol., 273:927-948, 1997, is provided in Table 2 below:

TABLE 2 CDR Loop* Kabat AbM Chothia Contact L1 L24--L34 L24-L34 L24--L34L30--L36 L2 L50--L56 L50--L56 L50--L56 L46--L55 L3 L89--L97 L89--L97L89--L97 L89--L96 H1 H13--H35B H26--H35B H26--H32..34 H30--H35B (KabatNumbering) H1 H31--H35 H26--H35 H26--H32 H30--H35 (Chothia Numbering) H2H50-H65 H50-H58 H52--H56 H47--H58 H3 H95--H102 H95--H102 H95--H102H93--H101 *L = light chain; H = heavy chainCDRs may also be identified by following a set of rules such as thoseset forth in Table 3 below (as described athttp://www.bioinf.org.uk/abs/#cdrid):

TABLE 3 CDR*/Feature Typical Characteristic of Feature** CDR-L1 Startapproximately residue 24 Residues before typically Cys Residues aftertypically Trp (e.g., Trp-Tyr-Gln, Trp-Leu-Gln, Trp- Phe-Gln,Trp-Tyr-Leu) Length 10 to 17 residues CDR-L2 Start typically 16 residuesafter the end of L1 Residues before typically Ile-Tyr, Val-Tyr, Ile-Lys,or Ile-Phe Length typically seven (7) residues CDR-L3 Start typically 33residues after end of L2 Residues before typically Cys Length typicallyPhe-Gly-X-Gly Residues after 7 to 11 residues CDR-H1 Start Approximatelyresidue 26 (typically four (4) residues after a Cys) (Chothia/AbMdefinition); Kabat definition starts 5 residues later Residues beforetypically Cys-X-X-X Residues after typically Trp (e.g., Trp-Val,Trp-Ile, Trp-Ala) Length 10 to 12 residues (AbM definition); Chothiadefinition excludes the last four (4) residues CDR-H2 Start typically 15residues after the end of Kabat/AbM definition of CDR-H1 Residues beforetypically Leu-Glu-Trp-Ile-Gly Residues after typicallyLys/Arg-Leu/Ile/Val/Phe/Thr/Ala- Thr/Ser/Ile/Ala Length Kabat definition16 to 19 residues; AbM (and recent Chothia) definition 9 to 12 residuesCDR-H3 Start typically 33 residues after end of CDR-H2 (typically two(2) residues following a Cys) Residues before typically Cys-X-X(typically Cys-Ala-Arg) Residues after typically Trp-Gly-X-Gly Lengthtypically 3 to 25 residues *L = light chain; H = heavy chain; **X = anyamino acid

These systems for identifying CDRs are merely exemplary and others maybe suitable, as would be understood by one of ordinary skill in the art.CDRs thus identified may be used to identify suitable binding agents.For instance, equivalents of one or more of the monoclonal antibodies1E4, 1G10, and for 1G1 may be binding agents comprising the amino acidsequences. Such CDRs may also be combined with one another in any orderand/or combination to form hybrid and/or fusion binding agents and/orinserted into the other heavy and/or light chain variable regions usingstandard techniques. The amino acid sequences shown in Table 1, and/orany one or more fragments and/or derivatives thereof, may be encoded byany of several nucleic acid sequences. These nucleic acid sequences mayalso be used to identify and or prepare (e.g., as nucleic acidmolecules) suitable binding agents. For example, one of ordinary skillin the art may devise nucleotide sequences encoding any such amino acidsequences with reference to any one or more of Tables 1-7 herein.Exemplary nucleotide sequences encoding the light chain variable regionsof 1E4, 1G10, and IG1 may be those shown in Table 1. Any of thenucleotide sequences shown in Table 1, and/or fragments and/orderivatives thereof, may be combined with one another in any orderand/or combination to encode hybrid and/or fusion binding agents and/orinserted into the other nucleic acid sequences encoding light and/orheavy chain variable regions (and/or fragments and/or derivativesthereof). Exemplary fragments may be, for example, any nucleic acidsequence encoding any of the amino acid sequences shown in Table 1,and/or any fragment and/or derivative thereof (e.g., one or more CDRsthereof). Putative CDRs of the monoclonal antibodies 1E4, 1G10 and 1G1are listed in Table 4. These CDRs were identified using the schemes setforth in, Kabat et al., “Sequences of Proteins of ImmunologicalInterest,” 5th Ed., Public Health Service, National Institutes ofHealth, Bethesda, Md., NIH publication No. 91-3242 (1991), andAl-Lazikani et al, “Standard conformations for the canonical structuresof immunoglobulins,” J. Mol. Biol. 273:927-948, 1997.

TABLE 4 Kabat CDRs Chotbia CDRs  (Kabat (Al-Lazikani CDR et al. 1991)et al. 1997) 1E4 CDRH1 DYGML GFTFSDY (SEQ ID NO.: 20) (SEQ ID NO.: 21)1E4 CDRH2 YISSGSSTIYYADRVKG SSGSST (SEQ ID NO.: 22) (SEQ ID NO.: 23)1E4 CDRH3 GTFAY GTFAY (SEQ ID NO.: 24) (SEQ ID NO.: 24) 1E4 CDRL1RSSQSLIYNNGNTYLH SQSLIYNNGNTY (SEQ ID NO.: 25) (SEQ ID NO.: 26)1E4 CDRL1 RSSQSLIYNKGNTYLH SQSLIYNKGNTY N33 to K (SEQ ID NO.: 70)(SEQ ID NO.: 71) 1E4 CDRL1 RSSQSLIYNNKNTYLH SQSLIYNNKNTY G34 to K(SEQ ID NO.: 72) (SEQ ID NO.: 73) 1E4 CDRL1 ESSQLIYNNQNTYIN SQSLIYNNQTYG34 to Q (SEQ ID NO.: 74) (SEQ ID NO.: 75) 1E4 CDRL1 RSSQSLIYNNANTYLHSQSLIYNNANTY G34 to A (SEQ ID NO.: 76) (SEQ ID NO.: 77) 1E4 CDRL2KVSNRFS VS (SEQ ID NO.: 27) (SEQ ID NO.: 28) 1E4 CDRL3 SQSTHVPFT STHVPF(SEQ ID NO.: 29) (SEQ ID NO.: 30) 1G1 CDRH1 DDYMH GFNIKDD(SEQ ID NO.: 31) (SEQ ID NO.: 32) 1G1 CDRH2 WIDPENGHTKYASKFQG DPENGH(SEQ ID NO.: 33) (SEQ ID NO.: 34) 1G1 CDRH3 LRHYYGSSYVSPHYYLRHYYGSSYVSPHYY (SEQ ID NO.: 35) (SEQ ID NO.: 36) 1G1 CDRL1 KASQNVGPNVASQNVGPN (SEQ ID NO.: 37) (SEQ ID NO.: 38) 1G1 CDRL2 SASYRYS SAS(SEQ ID NO.: 39) (SEQ ID NO.: 40) IG1 CDRL3 QQYNNYPYT YNNYPY(SEQ ID NO.: 41) (SEQ ID NO.: 42) 1G10 CDRH1 DYYMN GYTFTDY(SEQ ID NO.: 43) (SEQ ID NO.: 44) 1G10 CDHR2 DINPNNGDTSYNQKFKG NPNNGD(SEQ ID NO.: 43) (SEQ ID NO:: 44) 1G10 CDHR3 GGVLRYPYYYVMDYGGVLRYPYYYVMDY (SEQ ID NO.: 47) (SEQ ID NO.: 48) 1G10 CDRL1RSNKSLLHRNGNTYLY NYSLLHRNGNTY (SEQ ID NO.: 49) (SEQ ID NO.: 50)1G10 CDRL2 RMSNLAS RMS (SEQ ID NO.: 51) (SEQ ID NO.: 52) 1G10 CDRL3MQHLEFPFT HLEFPF (SEQ ID NO.: 53) (SEQ ID NO.: 54)

In some embodiments, the binding agent may comprise the amino acidsequences set forth in Table 4 above. Subgroups of these combinationsand/or other combinations of the CDRs shown in Table 4 may also besuitable, as would be understood by those of in the art. In one example,various combinations of the above CDRs may be used to provide caninizedantibodies.

The variable region sequences described herein (which may comprisefragments and/or derivatives thereof), including but not limited to theamino acid sequences shown in Table 1 (and/or fragments and/orderivatives thereof) and or the nucleotide sequences shown in Table 1(and/or fragments and/or derivatives thereof) may be used in combinationwith one or more amino acid sequences and/or nucleotide sequencesencoding one or more constant chains (and/or a fragment and/orderivatives thereof) of an antibody molecule. For instance, the variableregion amino acid sequences shown in Table 1 may be joined to theconstant regions of any antibody molecule of the same or a differentspecies (e.g., human, goat, rat, sheep, chicken) of that from which thevariable region amino acid sequence was derived.

Deamidation of asparagine residues to aspartic acid or isoaspartic acidis a common post-translational modification to proteins. Deamidation mayoccur with higher frequency when the asparagine is part of anasparagine-glycine dipeptide (Asp-Gly or N-G; the “NG” sequence).Deamidation may have detrimental effects on proteins. In one example,deamidation may potentially cause a change in the three-dimensionalstructure of a protein. In another example, for an antibody, deamidationin a region that affects binding to an antigen (e.g., variable regionsand or CDRs) may potentially cause lower or loss of antibody binding tothe antigen.

Accordingly, it may be beneficial to substitute amino acid residuespotentially susceptible to post-translational deamidation with thoseless or not susceptible. In one example, asparagine 33 (N33) and orglycine 34 (G34) of SEQ ID NO.: 3 (light chain variable region (V_(L))of 1E4) may be substituted to modify the NG sequence (see, e.g., SEQ IDNOS. 71, 73, 75 and 77). SEQ ID NO.: 3 is shown below, with N33 and G34(an NG sequence) underlined:

(SEQ ID NO.: 3) DVVMTQNPLSLPVSLGDQASISCRSSQSLIYNNGNTYLHWYRQKPGQSPKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVEAEDLGVYFCSQSTH VPFTFGSGTKLEIKN33 and/or G34 may be substituted by, for example, any amino acid suchas alanine (A), glutamic acid (E), phenylalanine (F), histidine (H),isoleucine (I), lysine (K), leucine (L), methionine (M), proline (P),glutamine (Q), arginine (R), threontne (T), valine (V), and/or tyrosine(Y), in any combination. In some embodiments, N33 may be substituted by,for example, alanine (A), glutamic acid (E), phenylalanine (F),histidine (H), isoleucine (I), lysine (K), leucine (L), proline (P),glutamine (Q), arginine (R), threonine (T), valine (V) or tyrosine (Y).In some embodiments, G34 may be substituted by, for example, alanine(A), glutamic acid (E), phenylalanine (F), histidine (H), isoleucine(I), lysine (K), leucine (L), proline (P), glutamine (Q), arginine (R),valine (V), tryptophan (W) or tyrosine (Y) in any combination.

In one embodiment, N33 (of, e.g., SEQ ID NO.: 9) may be substituted bylysine (K) (N33K substitution). In particular embodiments, G34 (of,e.g., SEQ ID NO.: 9), may be substituted by lysine (K) (G34K), glutamine(Q) (G34Q), or alanine (A) (G34A). In some embodiments, thesubstitutions may include N33K and any of G34K, G34Q, or G34A. Othersubstitutions may also be suitable as would be understood by one ofordinary skill in the art.

In other embodiments, asparagine 33 (N33) and/or glycine 34 (G34) of SEQID NO.: 9 (light chain variable region (V_(L)) of 1G10), asparagine 55(N55) and/or glycine 56 (G56) of SEQ ID NO.: 11 (heavy chain variableregion (V_(H)) of 1G10), or asparagine 55 (N55) and or glycine 56 (G56)of SEQ ID NO.: 15 (heavy chain variable region (V_(H)) of 1G1) may besubstituted by any suitable amino acid. In another example, one or moreof asparagines 103 (N103), 183 (N183) and/or 270 (N270), and/or glycines104 (G104), 184 (G184) and/or 271 (G271) of SEQ ID NO.: 57 (canine IgGBheavy chain constant region) may be substituted by any suitable aminoacid. Additional information regarding certain substitutions isdescribed and tested in the Examples. And other substitutions may alsobe suitable, as may be determined by one of ordinary skill in the art.

The constant regions may be derived from any of for example, human(e.g., IgG (IgG1, IgG2, IgG3, IgG4), IgM, IgA (IgA1 and IgA2), IgD, andIgE), canine (e.g., IgG (IgGA, IgGB, IgGC, IgGD) IgA, IgD, IgE, andIgM), chicken (e.g., IgA, IgD, IgE, IgG, IgM, IgY), goat (e.g., IgG),mouse (e.g., IgA, IgG, IgD, IgE, IgM), pig (e.g., IgA, IgG, IgD, IgE,IgM), rat (e.g., IgA, IgG, IgD, IgE, IgM), feline (e.g., IgA, IgD, IgE,IgG, IgM) and/or a fragment and or derivative thereof (e.g., as chimericantibodies). For example, one or more of the amino acid sequences ofTable 1 and/or Table 4 may be adjoined or associated with a non-caninevariable and/or constant region (e.g., human) to produce a chimericantibody. A binding agent may, for example, comprise an amino acidsequence of any of those shown in Table 1 (and or fragments and/orderivatives thereof) and, for example, a canine antibody constantregion. Exemplary amino acid and nucleotide sequences of canine IgGBlight and heavy chain constant regions that may be utilized as describedherein are shown below in Table 5:

TABLE 5 Description Sequence Amino acid sequenceRNDAQPAVYLFQPSPDQLHTGSASVVCLLNSFYPKDINVKWKV of canine light chainDGVIQDTGIQESVTEQDKDSTYSLSSTLTMSSTEYLSHELYSC constant regionEITHKSLPSTLIKSFQRSECQRVD (SEQ ID NO.: 55) Codon-optimizedCGTAACGACGCCCAGCCTGCCGTGTATCTGTTCCAGCCCTCCC nucleotide sequenceCCGATCAGCTGCATACCGGGTCCGCCTCAGTGGTGTGCCTGCT encoding SEQ IDGAACAGTTTCTACCCCAAGGACATCAATGTGAAGTGGAAAGTG NO:.: 55GACGGCGTCATCCAGGATACTGGCATCCAGGAGAGCGTCACCGAACAGGACAAAGATTCAACATATTCCCTGTCCAGCACCCTGACAATGTCTAGTACTGAGTACCTGAGCCACGAACTGTATTCTTGCGAGATTACCCATAAGAGCCTGCCATCCACCCTGATTAAGAGTTTCCAGCGTTCCGAATGCCAGAGAGTCGAT (SEQ ID NO: 56) Amino acid sequenceRTDAQPAVYLFQPSPDQLHTGSASVVCLLNSFYPKDINVKWKV of canine lightDGVIQDTGIQESVTEQDKSDTYSLSSTLTMSSTEYLSHELYSC chain constant regionEITHKSLPSTLIKSFQRSECQRVD (SEQ ID NO: 78) N2 to T Amino acid sequenceRNDAQPAVYLFQPSPDQLHTGSASVVCLLSSFYPKDINVKWKV of canine lightDGVIQDTGIQESVTEQDKDSTYSLSSTLTMSSTEYLSHELYSC chain constant regionEITHKSLPSTLIKSFQRSECQRVD (SEQ ID NO: 79) N30 to S Amino acid sequenceRTDAQPAVYLFQPSPDQLHTGSASVVCLLNSFYPKDINVKWKV of canine lightDGVIQDTGIQESVTEQDKDSTYSLSSTLTMSSTEYLSHELYSC chain constant regionEITHKSLPSTLIKSFQRSECQRVD (SEQ ID NO: 78) N2 to, T, N30 to SAmino acid sequence ASTTAPSVFPLAPSCGSTSGSTVALACLVSGYFPEPVTVSWNSof canine IgGB GSLTSGVHTFPSVLQSSGLYSLSSMVTVPSSRWPSETFTCNVAheavy chain constant HPASKTKVDKPVPKRENGRVPRPPDCPKCPAPEMLGGPSVFIF regionPPKPKDTLLIARTPEVTCVVVDLDPEDPEVQISWFVDGKQMQTAKTQPREEQFNGTYRVVSVLPIGHQDWLKGKQFTCKVNNKALPSPIERTISKARGQAHQPSVYVLPPSREELSKNTVSLTCLIKDFFPPDIDVEWQSNGQQEPESKYRTTPPQLDEDGSYFLYSKLSVDKSRWQRGDTFICAVMHEALHNHYTQKSLSHSPGK (SEQ ID NO: 57) Codon-optimizedGCGTCAACTACCGCTCCCTCCGTCTTCCCTCTGGCTCCTTCAT nucleotide sequenceGTGGTTCAACAAGTGGCAGTACCGTCGCCCTGGCTTGCCTGGT encoding SEQ IDGTCAGGGTACTTCCCTGAGCCAGTCACCGTGTCCTGGAACAGC NO.: 57GGGTCTCTGACAAGTGGTGTCCACACTTTTCCTTCAGTGCTGCAGTCCAGCGGTCTGTATTCCCTGTCTAGTATGGTCACTGTGCCATCATCCAGATGGCCCAGCGAAACTTTCACCTGTAACGTGGCACATCCAGCCTCTAAGACCAAAGTGGACAAGCCCGTGCCTAAACGAGAGAATGGAAGGGTGCCTCGACCACCTGATTGCCCAAAGTGTCCAGCACCAGAAATGCTGGGAGGACCATCCGTGTTCATCTTTCCACCCAAGCCTAAAGACACACTGCTGATTGCTAGGACCCCAGAGGTGACATGCGTGGTCGTGGACCTGGATCCCGAGGACCCTGAAGTCCAGATCAGCTGGTTCGTGGATGGGAAGCAGATGCAGACAGCAAAAACTCAGCCAAGGGAGGAACAGTTTAATGGTACTTACCGGGTCGTGTCTGTGCTGCCCATTGGCCACCAGGACTGGCTGAAGGGAAAACAGTTTACCTGCAAGGTGAACAACAAGGCTCTGCCTTCCCCAATCGAGCGAACAATTAGCAAGGCTCGTGGCCAGGCACATCAGCCCAGCGTCTACGTGCTGCCTCCATCCCGAGAGGAACTGAGCAAGAACACTGTGTCTCTGACCTGTCTGATCAAAGATTTCTTTCCCCCTGACATTGATGTGGAGTGGCAGTCTAATGGACAGCAGGAGCCTGAGAGTAAGTATCGGACCACACCACCCCAGCTGGACGAAGATGGCAGTTACTTCCTGTATAGTAAGCTGTCAGTGGACAAATCCAGATGGCAGCGCGGAGATACCTTCATCTGTGCCGTGATGCACGAAGCACTGCACAATCACTACACACAGAAGTCACTGAGCCACTCTCCAGGGAAA(SEQ ID NO.: 58)

One of ordinary skill in the art would understand that the constantregions of binding agents that are antibodies may be encoded by SEQ IDNO.: 56 and/or 58 and/or derivative nucleotide sequences thereof. Theconstant regions of the binding agents may comprise the amino acidsequence of SEQ ID NO.: 55, 78, 79, 80 and for 57, and/or derivativeamino acid sequences thereof. In one example, nucleotide sequencesencoding the antibodies are constructed into a vector system, and thenexpressed in host cells. In one example, the host cells am culturedcells. In one example, the vector system is used in mammalian culturedcells under conditions where the antibodies are expressed. Example 2describes an example of this.

In some applications, the binding agents may bind canine CD20 but havealtered ability to bind Fc receptors (e.g., CD16) as compared tostandard binding agents. In one example, the binding agents areantibodies that have modified glycosylation patterns. IgG molecules, forexample, typically contain N-linked oligosaccharides. Some IgG moleculescontain a biantennary complex-type oligosaccharide linked to theantibody heavy chain. In human IgG, the oligosaccharide is generallylinked to an asparagine residue at position 297 (N297) of the heavychain (in the constant/Fc region of the antibody heavy chain).Generally, a fucose is attached to the GLcNAC residue in theoligosaccharide that is nearest to N297. Absence of the fucose mayenhance the ability of the antibodies to mediate antibody-dependentcellular cytotoxicity (ADCC). Presumably, absence/removal of the fucoseenhances the ability of the antibody to interact with Fc receptors.Antibodies of this type may be referred to as “defucosylated”.Defucosylated antibodies may be produced using techniques describedherein and/or that may be known in the art. In some embodiments, anucleic acid sequence encoding an antibody may be expressed in a cellline that has modified glycosylation abilities (e.g., deleted, modifiedor lesser amount of fucosyl transferase) and fail to add the typicalfucose moieties. A variety of these cell lines are known. In someembodiments, the antibodies disclosed herein bind to canine CD20 butcontain defucosylated oligosaccharides. In one embodiment, theanti-canine CD20 antibody may contain a canine IgGB heavy chain constantregion. In some embodiments, the fucose moiety typically attached to theGLcNAC nearest N183 in canine IgGB heavy chain constant region (SEQ IDNO.: 57) is absent. Other techniques may also be used to alter thetypical fucosylation of antibodies and may be suitable, as would beunderstood by one of ordinary skill in the art.

The binding agents (e.g., antibodies) may include other modificationsthat may result in decreased interaction with Fc receptors (e.g., CD16).For instance, alternative or additional amino acid substitutions may bemade to the antibody molecules described herein. In one embodiment,canine IgGB heavy chain constant region (e.g., of SEQ ID NO.: 57) may besubstituted at one or both of amino acid residues M120 and L121. Incertain embodiments, either or both of these residues may be substitutedby alanine (A) or proline (P). In one embodiment, M (methionine) atposition 120 was substituted by P (proline) and L (leucine) at position121 was substituted by A (alanine), as shown below:

(SEQ ID NO.: 81)  ASTTAPSVFPLAPSCGSTSGSTVALACLVSGYFPEPVTVSWNSGSLTSGVHTFPSVLQSSGLYSLSSMVTVPSSRWPSETFTCNVAHPASKTKVDKPVPKRENGRVPRPPDCPKCPAPEPAGGPSVFIFPPKPKDTLLIARTPEVTCVVVDLDPEDPEVQISWFVDGKQMQTAKTQPREEQFNGTYRVVSVLPIGHQDWLKGKQFTCKVNNKALPSPIERTISKARGQAHQPSVYVLPPSREELSKNTVSLTCLIKDFFPPDIDVEWQSNGQQEPESKYRTTPPQLDEDGSYFLYSKLSNDKSRWQRGDTFICAVMHEALHNHYTQKSLSHSPGK.

In studies to characterize canine IgG containing M120P and L112 A,binding to CD16a was reduced as compared to canine IgGB that did notcontain the substitutions (i.e., the sequence as shown in SEQ ID NO.:57). Canine IgGA heavy chain was used as negative control, as itminimally or does not bind CD16a in our hands. We have also found thatcanine IgGD heavy chain also minimally or does not bind CD16a, whilecanine IgGB and IgGC heavy chains do bind CD16a (also, in B celldepletion experiments, as described in Example 3 and FIG. 6. 1E4-cIgGBand 1E4-cIgGC molecules did deplete B cells, while a 1E4-cIGA moleculedid not). Measured binding of the molecule containing M120P and L121Awas similar to the background level of binding measured for the IgGAmolecule.

In one embodiment, the canine IgGB heavy chain constant region (e.g., ofSEQ ID NO.: 57) N (asparagine) at position 183 was substituted by A. asshown below:

(SEQ ID NO.: 82)  ASTTAPSVFPLAPSCGSTSGSTVALACLVSGYFPEPVTVSWNSGSLTSGVHTFPSVLQSSGLYSLSSMVTVPSSRWPSETFTCNVAHPASKTKVDKPVPKRENGRVPRPPDCPKCPAPEPAGGPSVFIFPPKPKDTLLIARTPEVTCVVVDLDPEDPEVQISWFVDGKQMQTAKTQPREEQFNGTYRVVSVLPIGHQDWLKGKQFTCKVNNKALPSPIERTISKARGQAHQPSVYVLPPSREELSKNTVSLTCLIKDFFPPDIDVEWQSNGQQEPESKYRTTPPQLDEDGSYFLYSKLSNDKSRWQRGDTFICAVMHEALHNHYTQKSLSHSPGK.

In studies to characterize canine IgGB containing the N183Asubstitution, binding to CD16a was reduced as compared to canine IgGBthat did not contain the substitutions (i.e., the sequence as shown inSEQ ID NO.: 57). Canine IgGA heavy chain was used as negative control.Measured binding to CD16a of the molecule containing the N183Asubstitution was similar to the background level of binding measured forthe IgGA molecule.

In one embodiment, the canine IgGB heavy chain constant region (e.g., ofSEQ ID NO: 57) M at position 120 was substituted by A and L at position121 was substituted by A, as shown below:

(SEQ ID NO.: 83)  ASTTAPSVFPLAPSCGSTSGSTVALACLVSGYFPEPVTVSWNSGSLTSGVHTFPSVLQSSGLYSLSSMVTVPSSRWPSETFTCNVAHPASKTKVDKPVPKRENGRVPRPPDCPKCPAPEPAGGPSVFIFPPKPKDTLLIARTPEVTCVVVDLDPEDPEVQISWFVDGKQMQTAKTQPREEQFNGTYRVVSVLPIGHQDWLKGKQFTCKVNNKALPSPIERTISKARGQAHQPSVYVLPPSREELSKNTVSLTCLIKDFFPPDIDVEWQSNGQQEPESKYRTTPPQLDEDGSYFLYSKLSNDKSRWQRGDTFICAVMHEALHNHYTQKSLSHSPGK;

In studies to characterize canine IgGB containing M120A and L121A,binding to CD16a was reduced as compared to canine IgGB that did notcontain the substitutions (i.e., the sequence as shown in SEQ ID NO.:57). Canine IgGA heavy chain was used as negative control. Measuredbinding to CD16a of the molecule containing M120A and L121A wasdecreased compared to binding of IgGB that does not contain thesubstitutions. However, binding to CD16A of the M120A- andL121A-containing molecule was not reduced as much as for binding of theM120P and L121A molecule, or as much as for binding of the N183Amolecule.

In addition to the above molecules, the canine IgGB heavy chain constantregion (SEQ ID NO.: 57) may have other amino acid substitutions, forexample, at one or both of M120 and L121. In one embodiment, themolecule may have a M120A substitution. In one embodiment, the moleculemay have a L121A substitution. Other substitutions of M120 and/or L121,by A and/or P may be possible. In addition, any of these substitutionsmay be combined with the N183A substitution. Other modifications mayalso be suitable, as would be understood by one of ordinary skill in theart. Mixtures of antibodies having one or more of such modifications mayalso be suitable for various applications.

As described above, in some embodiments, binding agents may beantibodies. The term “antibody” or “antibodies” may refer to whole orfragmented antibodies in unpurified or partially purified form (e.g.,hybridoma supernatant, ascites, polyclonal antisera) or in purifiedform. A “purified” antibody may be one that is separated from at leastabout 50% of the proteins with which it is initially found (e.g., aspart of a hybridoma supernatant or ascites preparation). A purifiedantibody may be one that is separated from at least about 60%, 75%, 90%,or 95% of the proteins with which it is initially found. Suitablederivatives may also be fragments (e.g., Fab, F(ab′)₂ or single chainantibodies, like Fv, for example). The antibodies may be of any suitableorigin or form including, for example, murine (e.g., produced by marinehybridoma cells), or expressed as caninized antibodies, chimericantibodies, canine antibodies, and the like.

Methods of preparing and utilizing various types of antibodies arewell-known to those of skill in the art and would be suitable inpracticing the present invention see, for example, Harlow, et al.Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory, 1988;Harlow, et al., Using Antibodies: A Laboratory Manual, Portable ProtocolNo. 1, 1998; Kohler and Milstein, Nature, 256:495, 1975; Jones et al.,Nature, 321:522-525, 1986; Riechmann et al., Nature, 332:323-329, 1988;Presta, Curr. Op. Struct. Biol., 2:59:3-596, 1992; Verhoeyen et al.,Science, 239:1534-1536, 1988; Hoogenboom et al. J. Mol. Biol., 227:381,1991; Marks et al., J. Mol. Biol., 222:581, 1991; Cole et al.,Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, p. 77, 1985;Boerner et al., J. Immunol., 147(1):86-95, 1991; Marks et al.,Bio/Technology 10, 779-783, 1992; Lonberg et al., Nature 368:856-859,1994; Morrison, Nature 368:812-13, 1994; Fishwild et al., NatureBiotechnology 14, 845-51, 1996; Neuberger, Nature Biotechnology 14, 826,1996; Lonberg and Huszar, Intern. Rev. Immunol. 13:65-93, 1995; as wellas U.S. Pat. Nos. 4,816,567, 5,545,807, 5,545,806, 5,569,825, 5,625,126,5,633,425, and 5,661,016). In certain applications, the antibodies maybe contained within hybridoma supernatant or ascites and utilized eitherdirectly as such or following concentration using standard techniques.In other applications, the antibodies may be further purified using, forexample, salt fractionation and ion exchange chromatography, or affinitychromatography using Protein A, Protein G, Protein A/G, and/or Protein Lligands covalently coupled to a solid support such as agarose beads, orcombinations of these techniques. The antibodies may be stored in anysuitable format, including as a frozen preparation (e.g., −20° C. or−70° C.), in lyophilized form, or under normal refrigeration conditions(e.g., 4° C.). When stored in liquid form, a suitable buffer such asTris-buffered saline (TBS) or phosphate buffered saline (PBS) may beutilized.

The binding agents described herein are not in any way limited toantibodies. The binding agents may be any compound exhibiting similarbinding properties as antibodies (e.g., a mimetic). For example, anexemplary binding agent may be one that binds SEQ ID NO.: 1 and/or SEQID NO.: 2 (or a polypeptide comprising SEQ ID NO.: 1 and/or 2) and/orcan compete with a monoclonal antibody binding thereto (e.g., monoclonalantibodies 1E4, 1G10, and/or 1G1). In some embodiments, the bindingagent may exhibit substantially the same K_(d) in binding assays as thebinding agent (e.g., monoclonal antibody) to which it is being compared.For instance, the K_(d) of a particular binding agent may be measured byany suitable assay including but not limited, to the FACS assaydescribed in the Examples (e.g., FIG. 1). One binding agent may be saidto have “substantially the same K_(d)” as another where the measurementsare within about any of 1-20, 1-5, 5-10, 10-15, or 15-20 percent of oneanother.

Exemplary mimetics may include, for example, organic compounds thatspecifically bind canine CD20 (e.g., SEQ ID NO.: 1, 2, and/or 59, and/orpolypeptides comprising any such sequences) (see, e.g., Gebauer et al.,Curr. Opin. Chem. Biol. 13 (3):245-255, 2009). Such mimetics may be, forexample, an affibody (Nygren, et al., FEBS J. 275(11):2668-76, 2008),affilin (Ebersbach, et al., J. Mol. Biol. 372 (1):172-85, 2007), affitin(Krehenbrink et al., J. Mol. Biol. 383(5):1058-68, 2008), anticalin(Skerra, A., FEBS J. 275(11):2677-83, 2008), avimer (Silverman et al.,Nat. Biotechnol. 23(12): 1556-61, 2005), DARPin (Stumpp et al., DrugDiscov. Today 13(15-16):695-701, 2008), Fynomer (Grabulovski et al., J.Biol. Chem. 282(5):3196-3204, 2007), Kunitz domain peptide (Nixon etal., Curr. Opin. Drug Discov. Devel. 9(2):261-8, 2006), and/or amonobody (Koide et al., Methods Mol. Biol. 352:95-109, 2007). Othermimetics may also include, for example, derivative of an antibody (of,for example, the monoclonal antibody 1E4, 1G10, and/or 1G1) such as, forexample, an Fab, F(ab′)₂, Fab′ single chain antibody, Fv, single domainantibody, mono-specific antibody, bi-specific antibody, tri-specificantibody, multi-valent antibody, chimeric antibody, canine-humanchimeric antibody, canine-mouse chimeric antibody, antibody comprising acanine Fc, humanized antibody, human antibody, caninized, CDR-graftedantibody, shark antibody, nanobody (e.g., antibody consisting of asingle monomeric variable domain), camelid antibody (e.g., antibodies ofmembers of the Camelidae family), microbody, intrabody (e.g.,intracellular antibody), and/or de-fucosylated antibody and/orderivative thereof. Other binding agents are also provided herein aswould be understood by one of ordinary skill in the art.

In certain embodiments, preparations of binding agents are provided.Such preparations may comprise, for example, unpurified antibody asfound in hybridoma supernatants or ascites preparation, partiallypurified preparations, or purified preparations. Thus, provided hereinare antibody preparations containing one or more binding agents purifiedto about 50%, 60%, 75%, 90%, or 95% purity. Typically, such preparationsinclude a buffer such as phosphate- or tris-buffered saline (PBS or TBS,respectively). The preparations may also be formulated to containexcipients, like stabilizers, for example. The preparations may also, oralternatively comprise derivatives of such binding agents such as, forexample, Fab, F(ab′)₂ or single chain antibodies (Fv for example),caninized antibodies, chimeric antibodies, canine antibodies, and thelike. Where the binding agents are antibodies, nucleotide sequencesencoding the variable regions thereof may also be isolated from thehybridomas expressing the same cloned into expression vectors to producecertain antibody preparations (e.g., caninized antibodies). Methods forproducing such preparations are well-known in the art.

The skilled artisan has many suitable techniques for using the bindingagents (e.g., antibodies) described herein to identify biologicalsamples containing proteins that bind thereto. For instance, antibodiesmay be utilized to isolate canine CD20 protein using, for example,immunoprecipitation or other capture-type assay. This well-knowntechnique is performed by attaching the antibody to a solid support orchromatographic material (e.g., a bead coated with Protein A, Protein Gand/or Protein L). The bound antibody is then introduced into a solutioneither containing or believed to contain the CD20 protein (e.g., acanine B cell lysate). Canine CD20 protein may then bind to the antibodyand non-binding materials are washed away under conditions in which theCD20 protein remains bound to the antibody. The bound protein may thenbe separated from the antibody and analyzed as desired. Similar methodsfor isolating a protein using an antibody are well-known in the art. Thebinding agents (e.g., antibodies) may also be utilized to detect CD20protein within a biological sample. For instance, the antibodies may beused in assays such as, for example, flow cytometric analysis, ELISA,immunoblotting (e.g., western blot), in situ detection,immunocytochemistry and/or immunohistochemistry. Methods of carrying outsuch assays are well-known in the art.

To assist the skilled artisan in using the antibodies described herein,the same may be provided in kit format. A kit including such antibodiesand optionally other components necessary for using the antibodies todetect cells expressing canine CD20 is provided. The antibodies of thekit may be provided in any suitable form, including frozen, lyophilized,or in a pharmaceutically acceptable buffer such as TBS or PBS. The kitmay also include other reagents required for utilization of theantibodies in vitro or in vivo such as buffers (e.g, TBS, PBS), blockingagents (solutions including nonfat dry milk, normal sera, Tween-2.0Detergent, BSA, or casein), and/or detection reagents (e.g., goatanti-mouse IgG biotin, streptavidin-HRP conjugates, allophyeocyanin,B-phycoerythrin, R-phycoerythrin, peroxidase, detectable labels (e.g.,fluorosceins, like DyLight, Cy3, Cy5, FITC, HiLyte Fluor 555, HiLyteFluor 647; 5-carboxy-2,7-dichlorofluorescein, 5-Carboxyfluorescein(5-FAM). 5-HAT (Hydroxy Tryptamine), 5-Hydroxy Tryptamine (HAT), 6-JOE;6-carboxyfluorescein (6-FAM), FITC,6-carboxy-1,4-dichloro-2′,7′-dichloronorescein (TET),6-carboxy-1,4-dichloro-2′,4′,5′,7′-tetra-chlorofluorescein (HEX),6-carboxy-4′,5′-dichloro-2′,7′-dimethoxyfluorescein (JOE); Alexa fluors,like 350, 405, 430, 488, 500, 514, 532, 546, 555, 568, 594, 610, 633,635, 647, 660, 680, 700, 750; BODIPY fluorophores, like 492/515,493/503, 500/510, 505/515, 530/550, 542/563, 558/568, 564/570, 576/589,581/591, 630/650-X, 650/665-X, 665/676, FL, FL ATP, FI-Ceramide, R6G SE,TMR, TMR-X conjugate, TMR-X, SE, TR, TR ATP, TR-X SE; Rhodamines, like110, 123, B, B 200, BB, BG, B extra, 5-carboxytetramethylrhodamine(5-TAMRA), 5 GLD, 6-Carboxyrhodamine 6G, Lissamine, Lissamine RhodamineB, Phallicidine, Phalloidine, Red, Rhod-2, ROX (6-carboxy-X-rhodamine),5-ROX (carboxy-X-rhodamine), Sulphorhodamine B can C, Sulphorhodamine GExtra, TAMRA (6-carboxytetramethylrhodamine), Tetramethylatodamine(TRITC), WT, Texas Red, Texas Red-X) and other labels and/or stainingkits (e.g., ABC Staining Kit, Pierce). The kits may also include otherreagents and/or instructions for using the antibodies in commonlyutilized assays described above such as, for example, flow cytometricanalysis, ELISA, immunoblotting western blot), in situ detection,immunocytochemistry, immunohistochemistry. In one embodiment, thedetectable labels may be fixably attached to the binding agents. In oneexample, the detectable labels are fixably attached to the bindingagents by chemical bonds. In one example, the chemical bonds arecovalent chemical bonds. In one example, the detectable labels areconjugated to the binding agents.

In one embodiment, the kit provides a monoclonal antibody in purifiedform. In another embodiment, the monoclonal antibody may be provided inbiotinylated form either alone or along with an avidin-conjugateddetection reagent (e.g, antibody). In another embodiment, the kitincludes fluorescently-labelled antibodies that may be used to directlydetect canine CD20. Buffers and the like required for using any of thesesystems are well-known in the art and may be prepared by the end-user orprovided as a component of the kit. The kit may also include a solidsupport containing positive- and negative-control protein and/or tissuesamples. For example, kits for performing spotting or western blot-typeassays may include control cell or tissue lysates for use in SDS-PAGE ornylon or other membranes containing pre-fixed control samples withadditional space for experimental samples. Kits for visualization ofcanine CD20 in cells on slides may include pre-formatted slidescontaining control cell or tissue samples with additional space forexperimental samples.

The binding agents described herein and/or derivatives thereof may alsobe incorporated into compositions for use in vitro or in vivo. Theantibodies or derivatives thereof may also be fixably attached tofunctional effector moieties such as cytotoxic drugs or toxins, oractive fragments thereof such as diphtheria A chain, exotoxin A chain,ricin A chain, abrin A chain, curcin, crotin, phenomycin, enornycin,among others. Functional moieties may also include radiochemicals. Inone embodiment, the effector moieties may be fixably attached to thebinding agents. In one example, the detectable labels are fixablyattached to the binding agents by chemical bonds. In one example, thechemical bonds are covalent chemical bonds. In one example, the effectormoieties are conjugated to the binding agents.

The binding agents may be used alone or in combination with anotheragent for preventing and or treating disease. One such disease is B celllymphoma (e.g., diffuse large cell B cell lymphoma, follicular lymphoma,mucosa-associated lymphatic tissue lymphoma (MALT), small colilymphocytic lymphoma, chronic lymphocytic leukemia, mantel celllymphoma, Burkitt's lymphoma, mediastinal large B cell lymphoma,Waldenstrom macroglobulinemia, nodal marginal zone B cell lymphoma(NMZL), splenic marginal zone lymphoma (SMZL), intravascular largeB-cell lymphoma, primary effusion lymphoma, lymphomatoid granulomatosis,and the like), particularly in canine animals. The binding agents mayalso be combined with or used in conjunction with (e.g., as part of atreatment regimen) other anti-cancer agents such as, for example,cyclophosphamide (e.g., Cytoxan, Neosar), Adriamycindoxorubicin/hydroxydoxorubicin), vincristine (e.g., Oncovin), prednisone(e.g., Deltasone, Orasone), L-asparaginase, chlorambucil, lomustine(CCNU), cytosine arabinoside, mitoxantrone, and/or combinations thereof.A combination of such anti-cancer agents may refer to simultaneousand/or sequential administration.

The binding agents may also be used treat various autoimmune diseases.Example diseases may include, but are not limited to, autoimmunehemolytic anemia, immune-mediated thrombocytopenia, lupus, autoimmuneblistering diseases, immune-mediated arthritis and atopic dermatitis.

The antibodies described herein and or derivatives thereof may be usedin assays to determine the presence of a disease state in a patient, topredict prognosis, or to determine the effectiveness of achemotherapeutic or other treatment regimen. Expression profile assays,performed as described herein or as is otherwise known in the art, maybe used to determine the relative level of expression of CD20. The levelof expression may then be correlated with base (e.g., control) levels todetermine whether a particular disease is present within the patient,the patient's prognosis, or whether a particular treatment regimen iseffective. For example, if the patient is being treated with aparticular chemotherapeutic regimen, a decreased level of expression ofan immunogenic target in the patient's tissues (e.g., in peripheralblood, breast tissue biopsy) may indicate the regimen is decreasing thecancer load in that host. Similarly, if the level of expression isincreasing, this may indicate the regimen is not having the desiredeffect and another therapeutic modality may be selected.

It is also possible to use the antibodies described herein as reagentsin drug screening assays. The reagents may be used to ascertain theeffect of a drug candidate on the expression of the immunogenic targetin a cell line, or a cell or tissue of a patient. The expressionprofiling technique may be combined with high throughput screeningtechniques to allow rapid identification of useful compounds and monitorthe effectiveness of treatment with a drug candidate (see, for example,Zlokarnik et al., Science 279:84-8, 1998). Drug candidates may bechemical compounds, nucleic acids, proteins, antibodies, or derivativestherefrom, whether naturally occurring or synthetically derived. Drugcandidates thus identified may be utilized, among other uses, aspharmaceutical compositions for administration to patients or for use infurther screening assays.

The antibodies described herein may be prepared as an injectablepreparation, such as in suspension in a non-toxic parenterallyacceptable diluent or solvent. Suitable vehicles and solvents that maybe utilized include water, Ringer's solution, and isotonic sodiumchloride solution, TBS and PBS, among others. The formulations maycontain excipients, like stablizers, for example. In certainapplications, the antibodies are suitable for use in vitro. In otherapplications, the antibodies are suitable for use in vivo. Thepreparations suitable for use in either case are well-known in the artand will vary depending on the particular application.

Preparation of Binding Agents and Immunization

Also provided herein are canine CD20 polypeptides and/or fragmentsand/or derivatives thereof (collectively referred to herein as “canineCD20”), as well as methods of preparing and using the same. An exemplarycanine CD20 may comprise the amino acid sequence shown below:

(SEQ ID NO.: 59) NITISHFFKMENLNLIKAPMPYVDIHNCDPANPSEKNSLSIQYCGSI.Exemplary fragments of SEQ ID NO.: 59 may be SEQ ID NOS. 1 and/or 2.Thus, an exemplary canine CD20 may comprise SEQ ID NO. 59, SEQ ID NO.:1, and/or SEQ NO.: 2.

Canine CD20 typically exhibits the ability to induce anti-CD20antibodies in a host. Host animals generally are mammals, including butnot limited to a mouse, dog, cat, goat, sheep, human being, and thelike. In one example, the host may be a mouse. Administration of thecanine CD20 (for example, SEQ ID NOS. 1, 2 and or 59) results inproduction of anti-canine CD20 antibodies in the mouse. In one example,the host may be a dog and administration of the canine CD20 may resultin production of an immune response in the dog that may be specific forcells expressing CD20. The antibodies may be non-protective and/ornon-neutralizing, and or may be protective and/or neutralizingantibodies, following administration to the host animal.

In certain embodiments, the antibodies may be used to detect and forisolate canine CD20 and for to detect, isolate, and/or destroy cellsexpressing canine CD20. In certain embodiments, the canine CD20 mayshare amino acid sequence identity (e.g., any of about 90%, 95%, 98%,99%, or 99.9%) with other CD20 polypeptides (e.g., canine or otherwise).Any differences in the amino acid sequence between CD20 polypeptides aretypically but not necessarily phenotypically silent, but should beuseful for generating anti-CD20 immunity (e.g., inducing the productionof anti-CD20 antibodies in a host).

Nucleic acids encoding CD20 are also provided, along with variants ofsuch sequences (e.g., degenerate variants thereof). In certainembodiments, a nucleic acid molecule encoding canine CD20 may beinserted into one or more expression vectors, as discussed below ingreater detail. In such embodiments, canine CD20 may be encoded bynucleotides corresponding to the amino acid sequence. The particularcombinations of nucleotides that encode the various amino acids are wellknown in the art, as described in various references used by thoseskilled in the art (e.g., Lewin, B., Genes V, Oxford University Press,1994). The nucleotide sequences encoding canine CD20 may be ascertainedwith reference to Table 6, for example. Nucleic acid variants may useany combination of nucleotides that encode the polypeptide of interest.

TABLE 6 Phe (F) TTT Ser (S) TCT Tyr (Y) TAT Cys (C) TGT TTC TCC TAC TGCLeu (L) TTA TCA TERM TAA TERM TGA TTG TCG TAG Trp (W) TGG CTT Pro (P)CCT His (H) CAT Arg (R) CGT CTC CCC CAC CGC CTA CCA Gln (Q) CAA CGA CTGCCG CAG CGG Ile (I) ATT Thr (T) ACT Asn (N) AAT Ser (S) AGT ATC ACC AACAGC ATA ACA Lys (K) AAA Arg (R) AGA Met (M) ATG ACG AAG AGG Val (V) GTTAla (A) GCT Asp (D) GAT Gly (G) GGT GTC GCC GAC GGC GTA GCA Glu (E) GAAGGA GTG GCG GAG GGG

Modified CD20 may comprise at least one amino acid substitution,insertion, and/or deletion. Modified CD20 will typically remainsubstantially non-toxic and/or elicit neutralizing antibodies uponadministration to a host. Such antibodies may bind to the same epitopeas antibodies elicited following administration of another CD20 to ahost. As described herein, canine CD20 may be useful in immunogeniccompositions or vaccines for prevention and/or treatment of conditionsfor which targeting cells expressing CD20 would be beneficial (e.g.,cancer such as B cell lymphoma). Suitable modifications may introduceconservative changes in the amino acid sequence of canine CD20.Conservative amino acid substitutions may involve a substitution of anative amino acid residue with a non-native residue such that there islittle or no effect on the size, polarity, charge, hydrophobicity, orhydrophilicity of the amino acid residue at that position and, inparticular, does not result in decreased immunogenicity. Suitableconservative amino acid substitutions are shown in Table 7.

TABLE 7 Preferred Original Conservative Residues Exemplary ConservativeSubstitutions Substitution Ala Val, Leu, Ile Val Arg Lys, Gln, Asn LysAsn Gln Gln Asp Glu Glu Cys Ser, Ala Ser Gln Asn Asn Glu Asp Asp GlyPro, Ala Ala His Asn, Gln, Lys, Arg Arg Ile Leu, Val, Met, Ala, Phe,Norleucine Leu Leu Norleucine, Ile, Val, Met, Ala, Phe Ile Lys Arg, 1,4Diamino-butyric Acid, Gln, Asn Arg Met Leu, Phe, Ile Leu Phe Leu, Val,Ile, Ala, Tyr Leu Pro Ala Gly Ser Thr, Ala, Cys Thr Thr Ser Ser Trp Tyr,Phe Tyr Tyr Trp, Phe, Thr, Ser Phe Val Ile, Met, Leu, Phe, Ala,Norleucine LeuThe specific amino acid substitution selected may depend on the locationof the site selected.

The anti-CD20 antibodies, may be combined with one or morepharmaceutically acceptable carriers prior to administration to a host.A pharmaceutically acceptable carrier is a material that is notbiologically or otherwise undesirable, e.g., the material may beadministered to a subject, without causing any undesirable biologicaleffects or interacting in a deleterious manner with any of the othercomponents of the pharmaceutical composition in which it is contained.The carrier would naturally be selected to minimize any degradation ofthe active ingredient and to minimize any adverse side effects in thesubject, as would be well known to one of skill in the art.

Suitable pharmaceutical carriers and their formulations are describedin, for example, Remington's: The Science and Practice of Pharmacy,21^(st) Edition, David B. Troy, ed., Lippicott Williams & Wilkins(2005). Typically, an appropriate amount of apharmaceutically-acceptable salt is used in the formulation to renderthe formulation isotonic. Examples of the pharmaceutically-acceptablecarriers include, but are not limited to, sterile water, saline,buffered solutions like Ringer's solution, and dextrose solution. The pHof the solution is generally from about 5 to about 8 or from about 7 toabout 7.5. Other carriers include sustained-release preparations such assemipermeable matrices of solid hydrophobic polymers containingpolypeptides or fragments thereof. Matrices may be in the form of shapedarticles, e.g., films, liposomes or microparticles. It will be apparentto those persons skilled in the art that certain carriers may be morepreferable depending upon, for instance, the route of administration andconcentration of composition being administered. Carriers are thosesuitable for administration of polypeptides and/or fragments thereof tohumans or other subjects.

Pharmaceutical compositions may also include carriers, thickeners,diluents, buffers, preservatives, surface active agents, adjuvants,immunostimulants, in addition to the immunogenic polypeptide, or theanti-CD20 antibodies. Pharmaceutical compositions may also include oneor more active ingredients such as antimicrobial agents,antiinflammatory agents and anesthetics.

The compositions described herein may be administered to animals in vivoto generate an immune response against an immunogen SEQ ID NOS. 1, 2 and59), to detect cells expressing canine CD20, and or treat a diseasecondition in which cells expressing CD20 may need to be eliminated(e.g., B cell lymphoma). In certain embodiments, this disclosure alsoprovides binding agents such as antibodies (e.g., including monoclonalantibodies) useful in the isolation and or identification of cellsexpressing canine CD20 or a cell surface protein that reacts with suchbinding agents (e.g., B cells, B lymphoma cells, canine CD20) and/ortreatment and prevention of cancer in a mammal (e.g., a canine). Thus,in certain embodiments, the binding agent may be an antibody reactiveagainst canine. CD20 expressed on the cell surface. In some embodiments,the one or more binding agents (e.g., an antibody such as a monoclonalantibody) that binds to or reacts with canine CD20 at a region thereofwhich comprises SEQ ID NO.: 1, SEQ ID NO.: 2, and/or SEQ ID NO.: 59(and/or fragments and/or derivatives thereof).

Uses of Binding Agents

In some embodiments, methods for detecting canine cells using bindingagents are provided. In certain embodiments, cells expressing CD20 ontheir cell surface (e.g., B cell lymphoma) in an animal (e.g., acanine), can be detected by contacting a test biological sample with abinding agent or derivative thereof and detecting the binding agentbound to the biological sample or components thereof. In certainembodiments, the method may comprise comparing the amount of binding tothe test biological sample or components thereof to the amount ofbinding to a control biological sample or components thereof, whereinincreased binding to the test biological sample or components thereofrelative to the control biological sample or components thereofindicates the presence of a lymphoma cell in the test biological sample.In some embodiments, the biological sample may be canine blood or needleaspirates. Such methods are also provided in an in vivo and/or in vitroformat.

In some embodiments, methods for decreasing the viability and/or numberof cells expressing canine CD20 in a host using such binding agents arealso provided. Methods for treating one or more disease conditions(e.g., lymphoma) in a mammalian host comprising administering to themammal at least one or more effective doses of one or more bindingagents (and/or derivative(s) thereof) described herein are alsoprovided. In some embodiments, the binding agent is a monoclonalantibody or fragment or derivative thereof comprising one or more of theamino acid sequences shown in Tables 1, 4. and/or 5. The binding agentmay be administered in a dosage amount of about 1 to about 50 mg/kg ofbody weight of the mammal, about 1 to about 30 mg/kg, or about 1 toabout 15 mg/kg (e.g., about any of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,30, 35, or 40 mg/kg). In certain embodiments, the binding agent may beadministered to the mammal (e.g., intradermally, intravenously, orally,rectally) at about 1, 5 or 10 mg/kg one or more times. When multipledoses are administered, the doses may comprise about the same ordifferent amounts of binding agent in each dose. The doses may also beseparated in time from one another by the same or different intervals.For instance, the doses may be separated by about any of 6, 12, 24, 36,48, 60, 72, 84, or 96 hours, one week, two weeks, three weeks, onemonth, two months, three months, four months, five months, six months,seven months, eight months, nine months, 10 months, 11 months, 12months, 1.5 years, 2 years, 3 years, 4 years, 5 years, or any timeperiod before, after, and/or between any of these time periods. In someembodiments, the binding agents may be administered in conjunction withother agents (e.g., chemotherapeutic agents), as described above. Suchother agents may be administered about simultaneously with the bindingagents, or at a different time and/or frequency. Other embodiments ofsuch methods may also be appropriate as could be readily determined byone of ordinary skill in the art.

Generally, a dose of the monoclonal antibody that has the effect ofdecreasing the number, proliferation, detrimental effects, and so on, ofthe cancer cells in a dog, is called an effective dose.

Kits comprising any of the immunogens and/or binding agents describedherein, optionally also including instructions for using such immunogensand/or binding agents, are also provided, and may facilitate themethods. For example, a kit may contain a composition comprising abinding agent (e.g., mouse monoclonal antibody or chimeric antibodypreparation). The composition may further comprise a pharmaceuticallyacceptable carrier (e.g., phosphate-buffered saline) and may be insolution, frozen, lyophilized, or other suitable form. The kit may alsoinclude one or more control binding agents (e.g., a negative controlthat does not bind the target of the assay for which the kit isdesigned, or a positive control which may be supplied along with asample to which the positive control is known to bind) and orinstructions for use. As the kits could be used for in vitro or in vivoassays and/or treatments (e.g., a kit for administration to a mammal),the instructions may vary depending on the particular use for which thekit is designed. Other embodiments of such kits that could be providedwould be readily apparent to one of ordinary skill in the art.

It must be noted that, as used in the specification and the appendedclaims, the singular forms “a”, “an”, and “the” include plural referentsunless the context clearly dictates otherwise. Thus, for example,reference to a fragment may include mixtures of fragments and referenceto a pharmaceutical carrier or adjuvant may include mixtures of two ormore such carriers or adjuvants.

The terms “about”, “approximately”, and the like, when preceding a listof numerical values or range, refer to each individual value in the listor range independently as if each individual value in the list or rangewas immediately preceded by that term. The terms mean that the values towhich the same refer are exactly, close to, or similar thereto.

As used herein, a subject or a host is meant to be an individual. Thesubject or host may include domesticated animals, such as cats and dogs,livestock (e.g., cattle, horses, pigs, sheep, and goats), laboratoryanimals (e.g., mice, rabbits, rats, guinea pigs) birds, and/or humanbeings, for example. In some embodiments, the subject or host may be amammal such as a canine animal.

Optional or optionally means that the subsequently described event orcircumstance can or cannot occur, and that the description includesinstances where the event or circumstance occurs and instances where itdoes not. For example, the phrase optionally the composition cancomprise a combination means that the composition may comprise acombination of different molecules or may not include a combination suchthat the description includes both the combination and the absence ofthe combination (e.g., individual members of the combination).

Ranges may be expressed herein as from about one particular value,and/or to about another particular value. When such a range isexpressed, another aspect includes from the one particular value and/orto the other particular value. Similarly, when values are expressed asapproximations, by use of the antecedent about or approximately, it willbe understood that the particular value forms another aspect. It will befurther understood that the endpoints of each of the ranges aresignificant both in relation to the other endpoint, and independently ofthe other endpoint. Ranges (e.g., 90-100%) are meant to include therange per se as well as each independent value within the range as ifeach value was individually listed.

When the terms prevent, preventing, and prevention are used herein inconnection with a given treatment for a given condition (e.g.,preventing infection by Streptococcus sp.), it is meant to convey thatthe treated patient either does not develop a clinically observablelevel of the condition at all, or develops it more slowly and/or to alesser degree than he/she would have absent the treatment. These termsare not limited solely to a situation in which the patient experiencesno aspect of the condition whatsoever. For example, a treatment will besaid to have prevented the condition if it is given during exposure of apatient to a stimulus that would have been expected to produce a givenmanifestation of the condition, and results in the patient'sexperiencing fewer and/or milder symptoms of the condition thanotherwise expected.

All references cited within this disclosure are hereby incorporated byreference in their entirety. Certain embodiments are further describedin the following examples. These embodiments are provided as examplesonly and are not intended to limit the scope of the chains in any way.All references cited herein are hereby incorporated by reference. Abetter understanding of the present invention and of its many advantageswill be had from the following examples, given by way of illustration.

EXAMPLES Example 1 mAbs Reactive Against Canine CD20 A. Generation andSelection of Hybridomas

To generate mouse monoclonal antibodies against canine CD20, the 2^(nd)extracellular domain (ECD) of canine CO20 was cloned from canine PBMCcDNA, expressed as a mouse F_(c) fusion protein (“ECD2-mFc”), and usedas the immunogen. Canine ECD2-mFC has the amino acid sequences of SEQ IDNOS. 59 and 60, as shown below:

(SEQ ID NO.: 59) NITISHFFKMENLNLIKAPMPYVDIHNCDPANPSEKNSLSIQYCGSI; and,(SEQ ID NO.: 60) RSLEVLFQGPGSPPLKECPPCAAPDLLGGPSVFIFPPKIKDVLMISLSPMVTCVVVDVSEDDPDVQISWFVNNVEVHTAQTQTHREDYNSTLRVVSALPIQHQDWMSGKEFKCKVNNRALPSPIEKTISKPRGPVRAPQVYVLPPPAEEMTKKEFSLTCMITGFLPAEIAVDWTSNGRTEQNYKNTATVLDSDGSYFMYSKLRVQKSTWERGSLFACSVVHEGLHNHLTTKTISRSLGK.The immunogen contained a linear arrangement of SEQ ID NO.: 59 and SEQID NO. 60 and is set forth a SEQ ID NO.: 61:

(SEQ ID NO.: 61) NITISHFFKMENLNLIKAPMPYVDIHNCDPANPSEKNSLSIQYCGSIRSLEVLFQGPGSPPLKECPPCAAPDLLGGPSVFIFPPKIKDVLMISLSPMVTCVVVDVSEDDPDVQISWFVNNVEVHTAQTQTHREDYNSTLRVVSALPIQHQDWMSGKEFKCKVNNRALPSPIEKTISKPRGPVRAPQVYVLPPPAEEMTKKEFSLTCMITGFLPAEIAVDWTSNGRTEQNYKNTATVLDSDGSYFMYSKLRVQKSTWERGSLFACSVVHEGLHNHLTTKTISRSLGK.

Hybridomas were generated following immunization of mice with the SEQ IDNO.: 59/SEQ ID NO.: 60 fusion protein (SEQ ID NO.: 61). A primary ELISAscreen was carried out using ECD2-hFc fusion protein as the antigen.Positive hybridomas were then subjected to a secondary screen using amixture of fresh (CD20⁺) and cultured (CD20⁻) canine B-cell lymphomacells. Clones that displayed bifurcated FACS profiles were selected forfurther screening. Three mAbs expressed from hybridomas generated inthis approach (1E4, 1G1, and 1G10) were selected for furthercharacterization.

The relative affinities of the mouse monoclonal antibodies 1E4, 1G1, and1G10 for binding to canine CD20 was determined by fluorescent activatedcell sorting (FACS) using canine B cell lymphoma cells, which expresscanine CD20. The mAbs 1E4 and 1G10 were found to exhibit the highestrelative affinity to CD20: 1G10 (K_(d)=0.29 nm)>1E4 (K_(d)=0.97 nm)>>1G1(K_(d)=19.78 nm)) (FIG. 1).

In order to identify the epitope on canine CD20 that was bound by themouse monoclonal antibodies 1E4, 1G1, and 1G10 (none of which bind humanCD20), several expression constructs encoding hybrid versions of theoriginal immunogen (CD20 ECD2-mFc) were generated (FIG. 2A). The aminoacid sequences of the hybrid CD20 polypeptides are also shown below:

TABLE 7 Hybrid Amino Acid Sequence Canine CD20 ECD2NITISHFFKMENLNLIKAPMPYVDIHNCDPANPSEKNSL SIQYCGSI (SEQ ID NO.: 62)Hum-Can CD20 NITISHFFKMENLNFIRAHTPYINIYNCEPANPSEKNSP ECD2 V1STQYCYSI (SEQ ID NO.: 63) Hum-Can CD20NITISHFFKMENLNLIKAPMPYVNIYNCEPANPSEKNSP ECD2 V2STQYCYSI (SEQ ID NO.: 64) Hum-Can CD20NITISHFFKMENLNLIKAPMPYVDIHNCDPANPSEKNSP ECD2 V3STQYCYSI (SEQ ID NO.: 65) Hum-Can CD20NITISHFFKMENLNLIKAPMPYVNIYNCEPANPSEKNSL ECD2 V4SIQYCGSI (SEQ ID NO.: 66) Human CD20NIKISHFLKMESLNFIRAHTPYINIYNCEPANPSEKNSP STQYCYSI (SEQ ID NO.: 67)

As illustrated in FIG. 2A, the hybrid proteins expressed from thesevectors contained human CD20 sequences interspersed into canine CD20 indifferent portions of extracellular domain 2. This strategy- enabledidentification of the specific sequences in canine CD20 that each mAbbinds. Binding was tested using a standard ELISA protocol. Briefly,recombinant canine CD20 ECD2-mFc fusion protein and human/canine hybridvariants thereof were diluted in PBS and bound to a 96-well microtiterplate at 200 ng/well by overnight incubation at 4° C. The plate wasrinsed three times with PBST buffer, blocked with a solution of 3% BSAin PBS for one hour at 37° C., then rinsed once with PBST. Mousemonoclonal antibodies 1E4, 1G1, and 1G10 were diluted to a concentrationof 5 μg/ml in PBS and 50 μl of this dilution was applied to the platefor 1 hour at room temperature. The plate was then rinsed three timeswith PBST, and Jackson Immunoresearch goat anti-mouse-IgG lightchain-specific HRP conjugate (#115-035-174) diluted to 1:5000 in PBS (50μL) was added to each well, and the plate was incubated for 45 min atroom temperature. The plate was washed three times with PBST, then 100μl of SureBlueTMB substrate (KPL #52-00-03) was added to each well andthe plate was incubated for about 10 min at room temperature. The platewas read at 650 nm in a spectrophotometer.

The data presented in FIG. 2B demonstrate that mAbs 1E4 and 1G10 boundbetter to hybrid versions of cCD20 ECD2-mFc that contained the canineCD20 epitope DIHNCD (SEQ ID NO.: 2) in the ELISA assay, indicating thatthese mAbs bind a region of canine CD20 that contains the amino acidsequence DIHCD (SEQ ID NO.: 2). The mAb 1G1 bound better to CD20proteins that contained the canine CD20 epitope LIKAPMPYV (SEQ IDNO.: 1) in the ELISA assay, indicating that 1G1 binds to a region ofcanine CD20 that contains the amino acid sequence LIKAPMPYV (SEQ ID NO.:1).

Next, FACS was performed on canine PBMCs using purified 1E4-mAb (FIG.3). Canine PBMC were isolated by red blood cell lysis, labeled withpropidium iodide, and stained with 1E4 antibody (1 μg antibody/ml) andanti-mouse Fab-APC (1/200) from Jackson immunoresearch #115-136-146 asthe secondary antibody (secondary antibody alone was used as a negativecontrol). The primary FACS gate was on lymphocytes (left panels). Onlylive lymphocytes (those that did not stain with propidium iodide) wereincluded in the analysis (middle panels). Cells positive for antibodybinding were determined by setting a gate that included fewer than 1%positives in the negative control sample (upper right panel).Approximately 10 percent of lymphocytes were stained with 1E4 in thisexperiment, which is consistent with 1E4 specifically binding to CD20 onthe surface of canine B cells.

B. Sequencing of Variable Regions of 1E4, 1G1, and 1G10

The variable region DNAs from the murine monoclonal antibodies wereamplified by RT-PCR from RNA obtained from the hybridoma cell linesusing standard methods. Forward primers used to amplify heavy and lightchain variable region sequences were those reported in Chardés T. et alFEBS Letters. June 11; 452(3):386-94, 1999. Reverse primers used toamplify heavy and light chain variable region sequences are shown below:

5′-GCGTCTAGAAYCTCCACACACAGGRRCCAGTGGATAGAC-3′(heavy chain constant region primer (SEQ ID No.: 68));  and,5′-GCGTCTAGAACTGGATGGTGGGAAGATGG-3′ (light chainconstant region primer (SEQ ID NO.: 69)).The heavy and light chain variable region amplification products werethen cloned into a pcDNA3.1 vector and sequenced. The amino acid andnucleotide sequences of the 1E4, 1G1, and 1G10 variable regions areshown in Table 1.

Example 2 A. Expression of Canine Chimeric Antibodies 1E4-cIgGB andRituxan-cIgGB in CHO Cells

Genes encoding chimeric light and heavy antibody chains wereconstructed. A codon-optimized murine nucleotide sequence encoding thelight chain variable region of the 1E4 antibody (SEQ ID NO.: 5)(Table 1) was fused to a codon-optimized nucleotide sequence encodingthe light chain constant region from canine (SEQ ID NO.: 56) (Table 5),to produce a fusion gene encoding the chimeric antibody light chain.

In addition, a codon-optimized marine nucleotide sequence encoding theheavy chain variable region of the 1E4 antibody (SEQ ID NO.: 8)(Table 1) was fused to a codon-optimized nucleotide sequence encodingthe heavy chain constant region of canine IgGB (SEQ ID NO.: 58) (Table5), to produce a fusion gene encoding the canine chimeric antibody heavychain.

The chimeric light and heavy chains sequences were constructed into asingle plasmid expression vector. The vector was designed to containseparate mammalian transcription units (enhancer/promoter at 5′ end,poly A sequence at 3′ end) to express the chimeric light and heavychains. The 5′ coding region of each transcription unit also encoded aleader/signal sequence to provide for processing and assembly of theencoded proteins, and secretion of the anti-canine CD20 antibody, called1E4-cIgGB. The plasmid expression vector contained a separatetranscription unit encoding a protein that is selectable in mammaliancells. The plasmid expression vectors are described in WO 2009/080720(US 2011/0045536A) and WO 2010/022961. A separate, similar vectorencoding a canine chimeric version of an anti-human CD20 antibody,called Rituxan-cIgGB, was used as a control.

Both the plasmids encoding 1E4-cIgGB and control Rituxan-cIgGB weretransfected into CHO cells and stable pooled transfectants were selectedfor each as described in WO 2010/022961. Antibodies were produced fromthese stable antibody-expressing cell pools using standard fed-batchprotocols. Antibodies secreted from these cells were purified overProtein G Sepharose columns using a GE Healthcare AKTA-FPLC liquidchromatography system. The isolated antibody preparations were analyzedby SDS-PAGE and size-exclusion chromatography (see FIG. 4 for analysisof CHO-produced 1E4-cIgGB).

B. Modification of 1E4 Light Chain

Modifications of the antibodies described were also made using the aboveprocedures. Asparagine 33 (N33) or glycine 34 (G34) in theasparagine-glycine dipeptide sequence (Asp-Gly or N-G) of the lightchain variable region (V_(L)) of 1E4 (SEQ ID NO.: 3) were modified toremove a potential deamidation site. In various embodiments, N33 wassubstituted by alanine (A), glutamic acid (E), phenylalanine (F),histidine (H), isoleucine (I), lysine (K), leucine (L), proline (P),glutamine (Q), arginine (R), threonine (T), valine (V), or tyrosine (Y).In some embodiments, G34 was substituted by alanine (A), glutamic acid(E), phenylalanine (F), histidine (H), isoleucine (I), lysine (K),leucine (L), proline (P), glutamine (Q), arginine (R), valine (V), ortyrosine (Y). Whole antibodies (heavy plus light chains) containing oneof the above substitutions were tested by ELISA assay tier their abilityto bind canine CD20 ECD2 peptide (SEQ ID NO.: 62).

None of the above substitutions eliminated antibody binding to ECD2peptide and, in many cases, the effect of the substitution on antigenbinding was minor. FIG. 5 illustrates the results for some of theseantibodies: antibodies that contained one of substitution of N33 to K(lysine), G34 to K (lysine), G34 to Q (glutamine) or G34 to A (alanine).As shown in FIG. 5, none of these substitutions significantly affectedbinding to canine CD20.

Example 3 In Vivo Activity of the Chimeric Anti-Canine CD20 Antibody1E4-cIgGB

The efficacy of the chimeric antibody 1E4-cIgGB in depleting B cells wastested in vivo in a dose-response study. It has been shown that theanti-human CD20 antibody Rituximab (Rituxan®) does not cross-reactwith/bind to canine CD20 (Jubala et al., Vet Pathol., July;42(4):468-76, 2005; Impellizeri et al., Vet J., May; 171(3):556-8,2006). As such, a chimeric form of Rituxan containing a canine IgGB Fc(Rituxan-cIgGB) was cloned and expressed as described above in Example 2and used as a negative isotype control in this study. Pharmacodynamiceffects were measured over 59 days of treatment with 1E4-cIgGB atmultiple dose levels when administered by a single intravenous (IV)injection to naive healthy male Beagle dogs. Pre-study body weights andpre-study clinical pathology data (clinical chemistry and hematology)were utilized to randomize dogs into their respective treatment groups.The experimental design is shown below:

TABLE 6 Dose Group (mg/kg of animal (n = 5) Antibody body weight) 1Rituxan-cIgGB 10 2 1E4-cIgGB 0.1 3 1E4-cIgGB 1 4 1E4-cIgGB 10 51E4-cIgGB 30

On Day 1 of the study, a single dose (0.11, 10, or 30 mg/kg) of1E4-cIgGB or the isotype control antibody Rituxan-cIgGB (10 mg/kg) wasadministered to the animals via intravenous bolus injection. Blood wascollected from animals at Day 0 (pre-dose), Day 3, Day 7, Day 10, Day14, Day 28, Day 42, and Day 59. From these blood samples, clinicalpathology parameters were monitored and the percent of CD21-positivelymphocytes (B cells) in each dog were analyzed in triplicate by FACS onPBMC isolated from whole blood using a R-phycoerythrin (RPE)-conjugatedmouse anti-canine CD21 antibody (AbDserotec, cat # MCA 1781PE). Thepercentage of B-cells remaining at each time-point was calculated foreach dog by dividing the percentage of lymphocytes that were CD21positive at that time-point by the percentage that were CD21-positive atDay 0 (pre-dose). The averages of the percentages of B-cells remainingfor each treatment group were then calculated and graphed (FIG. 6).

All antibody doses were well-tolerated in the dogs. Marked,dose-dependent decreases in the percentages of CD21-positive cells (Bcells) were observed and sustained to Day 59 in beagles treated with 1,10, or 30 mg/kg of 1E4-cIgGB. Greater than 70% depletion of B-cells wasobserved at Day 7 in dogs treated with either 10 or 30 mg/kg 1E4-cIgGB.CD21-positive cells remained depleted out to Day 59, with 35% and >50%suppression in animals treated with 10 or 30 mg/kg 1E4-cIgGB,respectively. Dogs that were given a single dose of either the isotypecontrol antibody Rituxan-cIgGB (10 mg/kg) or of the lowest dose of1E4-cIgGB (0.1 mg/kg) did not show significant changes in percentages ofCD21-positive cells (B cells) during the study.

Example 4 Treatment of Dogs Having B Cell Lymphoma with the ChimericAnti-Canine CD20 Antibody 1E4-cIgGB

The 1E4 chimeric canine IgGB antibody described above is administered toBeagle male dogs having B cell lymphoma at an appropriate dose (e.g., 10mg/kg) via intravenous bolus injection. Blood is collected from animalsat various days including Day 0 (pre-dose) and, for example, Day 1, Day2, Day 3, Day 4, Day 7, Day 10, Day 14, Day 28, Day 42, and Day 59. Fromthese blood samples, clinical pathology parameters are monitored and thepercent of CD21-positive lymphocytes (B cells) in each dog are analyzedin triplicate by FACS on PBMC isolated from whole blood using aR-phycoerythrin (RPE)-conjugated mouse anti-canine CD21 antibody(AbDserotec, cat # MCA1781PE). The percentage of B-cells remaining ateach time-point is calculated for each dog by dividing the percentage ofCD21 positive lymphocytes at that time-point by the percentage that wereCD21-positive at Day 0 (pre-dose). The averages of the percentages ofB-cells remaining for each treatment group may then be calculated andgraphed to confirm that the treatment is effective.

While this disclosure may have been described in terms of the preferredembodiments, it is understood that variations and modifications willoccur to those skilled in the art. Therefore, it is intended that theappended claims cover all such equivalent variations that come withinthe scope of the invention as claimed.

1-20. (canceled)
 21. An isolated monoclonal antibody comprising at leastone set of variable region amino acid sequences selected from the groupconsisting of: a light chain variable region (LC-V) comprising thesequence of DIVMTQAAPSVPVTPGESVSISCRSX₁KX₂LLHRX₃X₄NTYLYWFLQRPGQSPQLLIYRMSNLASGVPDRFSGSGSGTAFTLRISRVEAEDVGVYYCMQHLEFPFTFG GGTKLEIK (SEQ IDNO.:17) and a heavy chain variable region (HC-V) comprising the sequenceof EVQLQQSGPELVKPGASVKISCKASGYTFTDYYMNWVKQSHGKSLEWIGDINPNNGDTSYNQKFKGKAPLTVDKSSSTAYMEVRSLTSEDSAVYFCARGGVLR YPYYYVMDYWGQGTSVTVSS(SEQ ID NO.: 11); where X₁ is any amino acid other than asparagine (N)when X₂ is serine (S) or threonine (T); where X₂ is any amino acid otherthan S or T when X₁ is N; where X₃ is an amino acid selected from thegroup consisting of alanine (A), glutamic acid (E), phenylalanine (F),histidine (H), isoleucine (I), lysine (K), leucine (L), proline (P),glutamine (Q), arginine (R), threonine (T), valine (V) and tyrosine (Y),when X₄ is glycine (G); and where X₄ is an amino acid selected from thegroup consisting of A, E, F, H, I, K, L, P, Q, R, V, Y, and tryptophan(W), when X₃ is N; an LC-V comprising the sequence ofDIVMTQAAPSVPVTPGESVSISCRSX₁KX₂LLHRX₃X₄NTYLYWFLQRPGQSPQLLIYRMSNLASGVPDRFSGSGSGTAFTLRISRVEAEDVGVYYCMQHLEFPFTFG GGTKLEIK (SEQ IDNO.:17) and a HC-V comprising the sequence ofEVQLQQSGPELVKPGASVKISCKASGYTFTDYYMNWVKQSHGKSLEWIGDINPNX₃X₄DTSYNQKFKGKAPLTVDKSSSTAYMEVRSLTSEDSAVYFCARGGVLRYPYYYVMDYWGQGTSVTVSS (SEQ ID NO.: 18), where X₁ is any amino acid otherthan N when X₂ is S or T; where X₂ is any amino acid other than S or Twhen X₁ is N; where X₃ is an amino acid selected from the groupconsisting of A, E, F, H, I, K, L, P, Q, R, T, V and Y, when X₄ is G;and where X₄ is an amino acid selected from the group consisting of A,E, F, H, I, K, L, P, Q, R, V, Y, and W, when X₃ is N; an LC-V comprisingthe sequence of DIVMTQAAP SVPVTPGESVSISCRSNKSLLHRNGNTYLYWFLQRPGQSPQLLIYRMSNLASGVPDRFSGSGSGTAFTLRISRVEAEDVGVYYCMQHLEFPFTFGG GTKLEIK (SEQ IDNO.: 9) and a HC-V comprising the sequence ofEVQLQQSGPELVKPGASVKISCKASGYTFTDYYMNWVKQSHGKSLEWIGDINPNX₃X₄DTSYNQKFKGKAPLTVDKSSSTAYMEVRSLTSEDSAVYFCARGGVLRYPYYYVMDYWGQGTSVTVSS (SEQ ID NO.: 18); where X₃ is an amino acidselected from the group consisting of A, E, F, H, I, K, L, P, Q, R, T, Vand Y, when X₄ is G; and where X₄ is an amino acid selected from thegroup consisting of A, E, F, H, I, K, L, P, Q, R, V, Y, and W, when X₃is N; and, an LC-V comprising the sequence ofDIVMTQSQKFMSRSVGDRVSVTCKASQNVGPNVAWYQQRPGQSPKPLIYSASYRYSGVPDRFTGSGSGTDFTLTISNVQSEDLAEYFCQQYNNYPYTFGGGTKLE IK (SEQ ID NO.:13) and a HC-V comprising the sequence ofEVQLQQSGAELVRPGASVKLSCTASGFNIKDDYMHWVKQRPEQGLEWIGWIX₅X₆EX₃X₄HTKYASKFQGKATITADTSSNTAYLQLSSLTSEDTAVYYCTSLRHYYGSSYVSPHYYWGQGTTLTVSS (SEQ ID NO.: 19); where X₃ is an amino acidselected from the group consisting of A, E, F, H, I, K, L, P, Q, R, T, Vand Y, when X₄ is G; where X₄ is an amino acid selected from the groupconsisting of A, E, F, H, I, K, L, P, Q, R, V, Y, and W, when X3 is N;where X₅ is any amino acid other than aspartic acid (D); and where X₆ isany amino acid other than P; and wherein the antibody binds canine CD20with an affinity (K_(d)) of at least 20 nM.
 22. The monoclonal antibodyof claim 21, wherein the antibody comprises at least one light chainimmunoglobulin constant region amino acid sequence from canine, and atleast one heavy chain immunoglobulin constant region amino acid sequencefrom canine.
 23. The monoclonal antibody of claim 22, wherein the atleast one light chain immunoglobulin constant region amino acid sequencefrom canine comprises an amino acid sequence selected from the groupconsisting of: (SEQ ID NO.: 55)RNDAQPAVYLFQPSPDQLHTGSASVVCLLNSFYPKDINVKWKVDGVIQDTGIQESVTEQDKDSTYSLSSTLTMSSTEYLSHELYSCEITHKSLPSTLIKS FQRSECQRVD,(SEQ ID NO.: 78) RTDAQPAVYLFQPSPDQLHTGSASVVCLLNSFYPKDINVKWKVDGVIQDTGIQESVTEQDKDSTYSLSSTLTMSSTEYLSHELYSCEITHKSLPSTLIKS FQRSECQRVD,(SEQ ID NO.: 79) RNDAQPAVYLFQPSPDQLHTGSASVVCLLSSFYPKDINVKWKVDGVIQDTGIQESVTEQDKDSTYSLSSTLTMSSTEYLSHELYSCEITHKSLPSTLIKS FQRSECQRVD, and(SEQ ID NO.: 80) RTDAQPAVYLFQPSPDQLHTGSASVVCLLSSFYPKDINVKWKVDGVIQDTGIQESVTEQDKDSTYSLSSTLTMSSTEYLSHELYSCEITHKSLPSTLIKSFQ RSECQRVD;

and wherein the at least one heavy chain immunoglobulin constant regionamino acid sequence from canine comprises an amino acid sequenceselected from the group consisting of: (SEQ ID NO.: 57)ASTTAPSVFPLAPSCGSTSGSTVALACLVSGYFPEPVTVSWNSGSLTSGVHTFPSVLQSSGLYSLSSMVTVPSSRWPSETFTCNVAHPASKTKVDKPVPKRENGRVPRPPDCPKCPAPEMLGGPSVFIFPPKPKDTLLIARTPEVTCVVVDLDPEDPEVQISWFVDGKQMQTAKTQPREEQFNGTYRVVSVLPIGHQDWLKGKQFTCKVNNKALPSPIERTISKARGQAHQPSVYVLPPSREELSKNTVSLTCLIKDFFPPDIDVEWQSNGQQEPESKYRTTPPQLDEDGSYFLYSKLSVDKSRWQRGDTFICAVMHEALHNHYTQKSLSHSPGK, (SEQ ID NO.: 81)ASTTAPSVFPLAPSCGSTSGSTVALACLVSGYFPEPVTVSWNSGSLTSGVHTFPSVLQSSGLYSLSSMVTVPSSRWPSETFTCNVAHPASKTKVDKPVPKRENGRVPRPPDCPKCPAPEPAGGPSVFIFPPKPKDTLLIARTPEVTCVVVDLDPEDPEVQISWFVDGKQMQTAKTQPREEQFNGTYRVVSVLPIGHQDWLKGKQFTCKVNNKALPSPIERTISKARGQAHQPSVYVLPPSREELSKNTVSLTCLIKDFFPPDIDVEWQSNGQQEPESKYRTTPPQLDEDGSYFLYSKLSVDKSRWQRGDTFICAVMHEALHNHYTQKSLSHSPGK, (SEQ ID NO.: 82)ASTTAPSVFPLAPSCGSTSGSTVALACLVSGYFPEPVTVSWNSGSLTSGVHTFPSVLQSSGLYSLSSMVTVPSSRWPSETFTCNVAHPASKTKVDKPVPKRENGRVPRPPDCPKCPAPEMLGGPSVFIFPPKPKDTLLIARTPEVTCVVVDLDPEDPEVQISWFVDGKQMQTAKTQPREEQFAGTYRVVSVLPIGHQDWLKGKQFTCKVNNKALPSPIERTISKARGQAHQPSVYVLPPSREELSKNTVSLTCLIKDFFPPDIDVEWQSNGQQEPESKYRTTPPQLDEDGSYFLYSKLSVDKSRWQRGDTFICAVMHEALHNHYTQKSLSHSPGK, and (SEQ ID NO.: 83)ASTTAPSVFPLAPSCGSTSGSTVALACLVSGYFPEPVTVSWNSGSLTSGVHTFPSVLQSSGLYSLSSMVTVPSSRWPSETFTCNVAHPASKTKVDKPVPKRENGRVPRPPDCPKCPAPEAAGGPSVFIFPPKPKDTLLIARTPEVTCVVVDLDPEDPEVQISWFVDGKQMQTAKTQPREEQFNGTYRVVSVLPIGHQDWLKGKQFTCKVNNKALPSPIERTISKARGQAHQPSVYVLPPSREELSKNTVSLTCLIKDFFPPDIDVEWQSNGQQEPESKYRTTPPQLDEDGSYFLYSKLSVDKSRWQRGDTFICAVMHEALHNHYTQKSLSHSPGK.


24. A method for treating a canine CD20-expressing lymphoma in a canineanimal comprising administering to the animal at least one effectivedose of the monoclonal antibody of claim
 21. 25. The method of claim 24,wherein the monoclonal antibody is administered in a dosage amount ofabout 1 to 50 mg/kg of body weight of the animal.
 26. The method ofclaim 24, wherein multiple doses are administered to the animal.
 27. Themethod of claim 24, wherein the monoclonal antibody is administered inconjunction with one or more chemotherapeutic agents.
 28. An isolatedmonoclonal antibody comprising a set of amino acid sequences selectedfrom the group consisting of: a. a heavy chain (H) complementarydetermining region (CDR) 1 (CDRH1) selected from the group consisting ofDYGML (SEQ ID NO.: 20) and GFTFSDY (SEQ ID NO.: 21), a CDRH2 selectedfrom the group consisting of YISSGSSTIYYADRVKG (SEQ ID NO.: 22) andSSGSST (SEQ ID NO.: 23), a CDRH3 comprising the sequence of GTFAY (SEQID NO.: 24), a light chain (L) CDR1 (CDRL1) selected from the groupconsisting of RSSQSLIYNNGNTYLH (SEQ ID NO.: 25), SQSLIYNNGNTY (SEQ IDNO.: 26), RSSQSLIYNKGNTYLH (SEQ ID NO.: 70), SQSLIYNKGNTY (SEQ ID NO.:71), RSSQSLIYNNKNTYLH (SEQ ID NO.: 72), SQSLIYNNKNTY (SEQ ID NO.: 73),RSSQSLIYNNQNTYLH (SEQ ID NO.: 74), SQSLIYNNQNTY (SEQ ID NO.: 75),RSSQSLIYNNANTYLH (SEQ ID NO.: 76), and SQSLIYNNANTY (SEQ ID NO.: 77), aCDRL2 selected from the group consisting of KVSNRFS (SEQ ID NO.: 27) andKVS (SEQ ID NO.: 28), and a CDRL3 selected from the group consisting ofSQSTHVPFT (SEQ ID NO.: 29) and STHVPF (SEQ ID NO.: 30); b. a CDRH1selected from the group consisting of DDYMEI (SEQ ID NO.: 31) andGFNIKDD (SEQ ID NO.: 32), a CDRH2 selected from the group consisting ofWIDPENGHTKYASKFQG (SEQ ID NO.: 33) and DPENGH (SEQ ID NO.: 34), a CDRH3comprising the sequence of LRHYYGSSYVSPHYY (SEQ ID NO.: 35), a CDRL1selected from the group consisting of KASQNVGPNVA (SEQ ID NO.: 37) andSQNVGPN (SEQ ID NO.: 38), a CDRL2 selected from the group consisting ofSASYRYS (SEQ ID NO.: 39) and SAS (SEQ ID NO.: 40), and a CDRL3 selectedfrom the group consisting of QQYNNYPYT (SEQ ID NO.: 41) and YNNYPY (SEQID NO.: 42); and c. a CDRH1 selected from the group consisting of DYYMN(SEQ ID NO.: 43) and GYTFTDY (SEQ ID NO.: 44), a CDRH2 selected from thegroup consisting of DINPNNGDTSYNQKFKG (SEQ ID NO.: 45) and NPNNGD (SEQID NO.: 46), a CDRH3 comprising the sequence of GGVLRYPYYYVMDY (SEQ IDNO.: 47), a CDRL1 selected from the group consisting of RSNKSLLHRNGNTYLY(SEQ ID NO.: 49) and NKSLLHRNGNTY (SEQ ID NO.: 50), a CDRL2 selectedfrom the group consisting of RMSNLAS (SEQ ID NO.: 51) and RMS (SEQ IDNO.: 52), and a CDRL3 selected from the group consisting of MQHLEFPFT(SEQ ID NO.: 53) and HLEFPF (SEQ ID NO.: 54); wherein the antibodycomprises at least one heavy chain polypeptide comprising a CDRH1, aCDRH2, and a CDRH3 sequentially, and at least one light chainpolypeptide comprising a CDRL1, a CDRL2, and a CDRL3 sequentially;wherein the at least one heavy chain polypeptide comprises frameworkregions from canine; wherein the at least one light chain polypeptidecomprises framework regions from canine; and wherein the antibody bindscanine CD20 with an affinity (K_(d)) of at least 20 nM.
 29. Themonoclonal antibody of claim 28, the antibody further comprising atleast one light chain immunoglobulin constant region amino acid sequencefrom canine comprising an amino acid sequence selected from the groupconsisting of: (SEQ ID NO.: 55)RNDAQPAVYLFQPSPDQLHTGSASVVCLLNSFYPKDINVKWKVDGVIQDTGIQESVTEQDKDSTYSLSSTLTMSSTEYLSHELYSCEITHKSLPSTLIKS FQRSECQRVD,(SEQ ID NO.: 78) RTDAQPAVYLFQP SPDQLHTGSASVVCLLNSFYPKDINVKWKVDGVIQDTGIQESVTEQDKDSTYSLSSTLTMSSTEYLSHELYSCEITHKSLPSTLIK SFQRSECQRVD,(SEQ ID NO.: 79) RNDAQPAVYLFQPSPDQLHTGSASVVCLLSSFYPKDINVKWKVDGVIQDTGIQESVTEQDKDSTYSLSSTLTMSSTEYLSHELYSCEITHKSLPSTLIKS FQRSECQRVD,  and(SEQ ID NO.: 80) RTDAQPAVYLFQPSPDQLHTGSASVVCLLSSFYPKDINVKWKVDGVIQDTGIQESVTEQDKDSTYSLSSTLTMSSTEYLSHELYSCEITHKSLPSTLIKS FQRSECQRVD;

and wherein the antibody further comprises at least one heavy chainimmunoglobulin constant region amino acid sequence from caninecomprising an amino acid sequence selected from the group consisting of:(SEQ ID NO.: 57) ASTTAPSVFPLAPSCGSTSGSTVALACLVSGYFPEPVTVSWNSGSLTSGVHTFPSVLQSSGLYSLSSMVTVPSSRWPSETFTCNVAHPASKTKVDKPVPKRENGRVPRPPDCPKCPAPEMLGGPSVFIFPPKPKDTLLIARTPEVTCVVVDLDPEDPEVQISWFVDGKQMQTAKTQPREEQFNGTYRVVSVLPIGHQDWLKGKQFTCKVNNKALPSPIERTISKARGQAHQPSVYVLPPSREELSKNTVSLTCLIKDFFPPDIDVEWQSNGQQEPESKYRTTPPQLDEDGSYFLYSKLSVDKSRWQRGDTFICAVMHEALHNHYTQKSLSHSPGK, (SEQ ID NO.: 81)ASTTAPSVFPLAPSCGSTSGSTVALACLVSGYFPEPVTVSWNSGSLTSGVHTFPSVLQSSGLYSLSSMVTVPSSRWPSETFTCNVAHPASKTKVDKPVPKRENGRVPRPPDCPKCPAPEPAGGPSVFIFPPKPKDTLLIARTPEVTCVVVDLDPEDPEVQISWFVDGKQMQTAKTQPREEQFNGTYRVVSVLPIGHQDWLKGKQFTCKVNNKALPSPIERTISKARGQAHQPSVYVLPPSREELSKNTVSLTCLIKDFFPPDIDVEWQSNGQQEPESKYRTTPPQLDEDGSYFLYSKLSVDKSRWQRGDTFICAVMHEALHNHYTQKSLSHSPGK, (SEQ ID NO.: 82)ASTTAPSVFPLAPSCGSTSGSTVALACLVSGYFPEPVTVSWNSGSLTSGVHTFPSVLQSSGLYSLSSMVTVPSSRWPSETFTCNVAHPASKTKVDKPVPKRENGRVPRPPDCPKCPAPEMLGGPSVFIFPPKPKDTLLIARTPEVTCVVVDLDPEDPEVQISWFVDGKQMQTAKTQPREEQFAGTYRVVSVLPIGHQDWLKGKQFTCKVNNKALPSPIERTISKARGQAHQPSVYVLPPSREELSKNTVSLTCLIKDFFPPDIDVEWQSNGQQEPESKYRTTPPQLDEDGSYFLYSKLSVDKSRWQRGDTFICAVMHEALHNHYTQKSLSHSPGK, and (SEQ ID NO.: 83)ASTTAPSVFPLAPSCGSTSGSTVALACLVSGYFPEPVTVSWNSGSLTSGVHTFPSVLQSSGLYSLSSMVTVPSSRWPSETFTCNVAHPASKTKVDKPVPKRENGRVPRPPDCPKCPAPEAAGGPSVFIFPPKPKDTLLIARTPEVTCVVVDLDPEDPEVQISWFVDGKQMQTAKTQPREEQFNGTYRVVSVLPIGHQDWLKGKQFTCKVNNKALPSPIERTISKARGQAHQPSVYVLPPSREELSKNTVSLTCLIKDFFPPDIDVEWQSNGQQEPESKYRTTPPQLDEDGSYFLYSKLSVDKSRWQRGDTFICAVMHEALHNHYTQKSLSHSPGK.


30. A method for treating a canine CD20-expressing lymphoma in a canineanimal comprising administering to the animal at least one effectivedose of the monoclonal antibody of claim
 28. 31. The method of claim 30,wherein the monoclonal antibody is administered in a dosage amount ofabout 1 to 50 mg/kg of body weight of the animal.
 32. The method ofclaim 30, wherein multiple doses are administered to the animal.
 33. Themethod of claim 30, wherein the monoclonal antibody is administered inconjunction with one or more chemotherapeutic agents.